mpp

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Allocation of Resources Without Limits or Throttling in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet through concurrent sponsored payments, denying service to legitimate payers once it is empty.

MPP.Methods.Tempo.FeePayerPolicy enforces its ceilings (max_gas, max_fee_per_gas, max_priority_fee_per_gas, the worst-case gas_limit * max_fee_per_gas <= max_total_fee budget cap, and a validity window) against one transaction at a time, and nothing accounts for exposure across concurrent requests. reserve_hash_atomic/2 is keyed on the transaction hash, so it prevents duplicate broadcast of the same signed transaction but not N distinct sponsored transactions carrying distinct expiring nonces. Committed sponsor exposure is therefore N times max_total_fee, bounded by nothing in the library, and the default 900 second validity window lets co-signed transactions stay broadcastable and uncounted for that entire period.

This issue affects mpp: from 0.2.0 before 0.12.0.

Workarounds

Disable Tempo fee sponsorship by setting "fee_payer" => false (the default), so the client pays its own gas and the sponsor wallet is never committed. Where sponsorship must stay enabled, lowering max_total_fee and max_validity_window_seconds reduces the exposure each concurrent request can commit and how long it stays outstanding, without bounding the aggregate.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Allocation of Resources Without Limits or Throttling in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet through concurrent sponsored payments, denying service to legitimate payers once it is empty.

MPP.Methods.Tempo.FeePayerPolicy enforces its ceilings (max_gas, max_fee_per_gas, max_priority_fee_per_gas, the worst-case gas_limit * max_fee_per_gas <= max_total_fee budget cap, and a validity window) against one transaction at a time, and nothing accounts for exposure across concurrent requests. reserve_hash_atomic/2 is keyed on the transaction hash, so it prevents duplicate broadcast of the same signed transaction but not N distinct sponsored transactions carrying distinct expiring nonces. Committed sponsor exposure is therefore N times max_total_fee, bounded by nothing in the library, and the default 900 second validity window lets co-signed transactions stay broadcastable and uncounted for that entire period.

This issue affects mpp: from 0.2.0 before 0.12.0.

Workarounds

Disable Tempo fee sponsorship by setting "fee_payer" => false (the default), so the client pays its own gas and the sponsor wallet is never committed. Where sponsorship must stay enabled, lowering max_total_fee and max_validity_window_seconds reduces the exposure each concurrent request can commit and how long it stays outstanding, without bounding the aggregate.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Allocation of Resources Without Limits or Throttling in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet through concurrent sponsored payments, denying service to legitimate payers once it is empty.

MPP.Methods.Tempo.FeePayerPolicy enforces its ceilings (max_gas, max_fee_per_gas, max_priority_fee_per_gas, the worst-case gas_limit * max_fee_per_gas <= max_total_fee budget cap, and a validity window) against one transaction at a time, and nothing accounts for exposure across concurrent requests. reserve_hash_atomic/2 is keyed on the transaction hash, so it prevents duplicate broadcast of the same signed transaction but not N distinct sponsored transactions carrying distinct expiring nonces. Committed sponsor exposure is therefore N times max_total_fee, bounded by nothing in the library, and the default 900 second validity window lets co-signed transactions stay broadcastable and uncounted for that entire period.

This issue affects mpp: from 0.2.0 before 0.12.0.

Workarounds

Disable Tempo fee sponsorship by setting "fee_payer" => false (the default), so the client pays its own gas and the sponsor wallet is never committed. Where sponsorship must stay enabled, lowering max_total_fee and max_validity_window_seconds reduces the exposure each concurrent request can commit and how long it stays outstanding, without bounding the aggregate.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Allocation of Resources Without Limits or Throttling in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet through concurrent sponsored payments, denying service to legitimate payers once it is empty.

MPP.Methods.Tempo.FeePayerPolicy enforces its ceilings (max_gas, max_fee_per_gas, max_priority_fee_per_gas, the worst-case gas_limit * max_fee_per_gas <= max_total_fee budget cap, and a validity window) against one transaction at a time, and nothing accounts for exposure across concurrent requests. reserve_hash_atomic/2 is keyed on the transaction hash, so it prevents duplicate broadcast of the same signed transaction but not N distinct sponsored transactions carrying distinct expiring nonces. Committed sponsor exposure is therefore N times max_total_fee, bounded by nothing in the library, and the default 900 second validity window lets co-signed transactions stay broadcastable and uncounted for that entire period.

This issue affects mpp: from 0.2.0 before 0.12.0.

Workarounds

Disable Tempo fee sponsorship by setting "fee_payer" => false (the default), so the client pays its own gas and the sponsor wallet is never committed. Where sponsorship must stay enabled, lowering max_total_fee and max_validity_window_seconds reduces the exposure each concurrent request can commit and how long it stays outstanding, without bounding the aggregate.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Allocation of Resources Without Limits or Throttling in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet through concurrent sponsored payments, denying service to legitimate payers once it is empty.

MPP.Methods.Tempo.FeePayerPolicy enforces its ceilings (max_gas, max_fee_per_gas, max_priority_fee_per_gas, the worst-case gas_limit * max_fee_per_gas <= max_total_fee budget cap, and a validity window) against one transaction at a time, and nothing accounts for exposure across concurrent requests. reserve_hash_atomic/2 is keyed on the transaction hash, so it prevents duplicate broadcast of the same signed transaction but not N distinct sponsored transactions carrying distinct expiring nonces. Committed sponsor exposure is therefore N times max_total_fee, bounded by nothing in the library, and the default 900 second validity window lets co-signed transactions stay broadcastable and uncounted for that entire period.

This issue affects mpp: from 0.2.0 before 0.12.0.

Workarounds

Disable Tempo fee sponsorship by setting "fee_payer" => false (the default), so the client pays its own gas and the sponsor wallet is never committed. Where sponsorship must stay enabled, lowering max_total_fee and max_validity_window_seconds reduces the exposure each concurrent request can commit and how long it stays outstanding, without bounding the aggregate.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Allocation of Resources Without Limits or Throttling in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet through concurrent sponsored payments, denying service to legitimate payers once it is empty.

MPP.Methods.Tempo.FeePayerPolicy enforces its ceilings (max_gas, max_fee_per_gas, max_priority_fee_per_gas, the worst-case gas_limit * max_fee_per_gas <= max_total_fee budget cap, and a validity window) against one transaction at a time, and nothing accounts for exposure across concurrent requests. reserve_hash_atomic/2 is keyed on the transaction hash, so it prevents duplicate broadcast of the same signed transaction but not N distinct sponsored transactions carrying distinct expiring nonces. Committed sponsor exposure is therefore N times max_total_fee, bounded by nothing in the library, and the default 900 second validity window lets co-signed transactions stay broadcastable and uncounted for that entire period.

This issue affects mpp: from 0.2.0 before 0.12.0.

Workarounds

Disable Tempo fee sponsorship by setting "fee_payer" => false (the default), so the client pays its own gas and the sponsor wallet is never committed. Where sponsorship must stay enabled, lowering max_total_fee and max_validity_window_seconds reduces the exposure each concurrent request can commit and how long it stays outstanding, without bounding the aggregate.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Allocation of Resources Without Limits or Throttling in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet through concurrent sponsored payments, denying service to legitimate payers once it is empty.

MPP.Methods.Tempo.FeePayerPolicy enforces its ceilings (max_gas, max_fee_per_gas, max_priority_fee_per_gas, the worst-case gas_limit * max_fee_per_gas <= max_total_fee budget cap, and a validity window) against one transaction at a time, and nothing accounts for exposure across concurrent requests. reserve_hash_atomic/2 is keyed on the transaction hash, so it prevents duplicate broadcast of the same signed transaction but not N distinct sponsored transactions carrying distinct expiring nonces. Committed sponsor exposure is therefore N times max_total_fee, bounded by nothing in the library, and the default 900 second validity window lets co-signed transactions stay broadcastable and uncounted for that entire period.

This issue affects mpp: from 0.2.0 before 0.12.0.

Workarounds

Disable Tempo fee sponsorship by setting "fee_payer" => false (the default), so the client pays its own gas and the sponsor wallet is never committed. Where sponsorship must stay enabled, lowering max_total_fee and max_validity_window_seconds reduces the exposure each concurrent request can commit and how long it stays outstanding, without bounding the aggregate.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Authentication Bypass by Capture-replay in ZenHive mpp allows an unauthenticated third party to obtain paid resources by replaying a transfer settled by an unrelated payer.

MPP.Methods.Tempo normally binds a settled TIP-20 TransferWithMemo to the specific challenge under verification through an attribution nonce carried in the memo. When a static "memo" is configured in method_config, check_matched_memo_binding/3 returns the match unconditionally and that binding is skipped, leaving only token, recipient, amount and the static memo value to match on. The static memo is echoed in every unauthenticated 402 response and Tempo transfers are public, so an attacker can take any matching transfer paid by a legitimate customer, request a fresh challenge for the same route, and present that transaction hash as a type="hash" credential. The hash path performs no sender or signature check tying the presenter to the wallet that broadcast the transfer.

This issue affects mpp: from 0.6.1 before 0.6.4.

Workarounds

Remove the static "memo" from the Tempo method_config so verification falls back to the default per-challenge attribution binding, which ties each settled transfer to the challenge being verified. Where a static memo must be kept, configure a dedup store (for example MPP.Tempo.ConCacheStore) with a TTL at least as long as the challenge expiry, which reduces unlimited replay to a race on the transaction hash rather than closing it.

Configurations

Only deployments that configure a static "memo" in the Tempo method_config are affected. Deployments using the default per-challenge attribution memo are not: that path binds each settled transfer to the challenge under verification and is single-use by construction.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Authentication Bypass by Capture-replay in ZenHive mpp allows an unauthenticated remote client to obtain paid resources by resubmitting one settled on-chain transfer.

MPP.Methods.EVM.verify/2 accepts a transaction-hash credential and matches a transfer purely on token, to and amount (ERC-20) or to and value (native). It binds the proof neither to the challenge being verified nor to any record of prior use, and the generic MPP.Plug dedup store keys on challenge.id, which is regenerated for every 402 response. On a static-price route, a single historical transfer matching the charge therefore satisfies an unbounded number of later charges, including transfers an attacker can read off a public block explorer.

This issue affects mpp: from 0.3.0 before 0.6.3.

Workarounds

Price each challenge uniquely (per-challenge or single-use amounts) so that a historical transfer cannot match a later charge, and keep challenge expiry short to narrow the window in which any given transfer stays useful. Deployments that can use the Tempo method for on-chain payments get per-challenge attribution binding instead.

Summary

Allocation of Resources Without Limits or Throttling in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet through concurrent sponsored payments, denying service to legitimate payers once it is empty.

MPP.Methods.Tempo.FeePayerPolicy enforces its ceilings (max_gas, max_fee_per_gas, max_priority_fee_per_gas, the worst-case gas_limit * max_fee_per_gas <= max_total_fee budget cap, and a validity window) against one transaction at a time, and nothing accounts for exposure across concurrent requests. reserve_hash_atomic/2 is keyed on the transaction hash, so it prevents duplicate broadcast of the same signed transaction but not N distinct sponsored transactions carrying distinct expiring nonces. Committed sponsor exposure is therefore N times max_total_fee, bounded by nothing in the library, and the default 900 second validity window lets co-signed transactions stay broadcastable and uncounted for that entire period.

This issue affects mpp: from 0.2.0 before 0.12.0.

Workarounds

Disable Tempo fee sponsorship by setting "fee_payer" => false (the default), so the client pays its own gas and the sponsor wallet is never committed. Where sponsorship must stay enabled, lowering max_total_fee and max_validity_window_seconds reduces the exposure each concurrent request can commit and how long it stays outstanding, without bounding the aggregate.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Authentication Bypass by Capture-replay in ZenHive mpp allows an unauthenticated third party to obtain paid resources by replaying a transfer settled by an unrelated payer.

MPP.Methods.Tempo normally binds a settled TIP-20 TransferWithMemo to the specific challenge under verification through an attribution nonce carried in the memo. When a static "memo" is configured in method_config, check_matched_memo_binding/3 returns the match unconditionally and that binding is skipped, leaving only token, recipient, amount and the static memo value to match on. The static memo is echoed in every unauthenticated 402 response and Tempo transfers are public, so an attacker can take any matching transfer paid by a legitimate customer, request a fresh challenge for the same route, and present that transaction hash as a type="hash" credential. The hash path performs no sender or signature check tying the presenter to the wallet that broadcast the transfer.

This issue affects mpp: from 0.6.1 before 0.6.4.

Workarounds

Remove the static "memo" from the Tempo method_config so verification falls back to the default per-challenge attribution binding, which ties each settled transfer to the challenge being verified. Where a static memo must be kept, configure a dedup store (for example MPP.Tempo.ConCacheStore) with a TTL at least as long as the challenge expiry, which reduces unlimited replay to a race on the transaction hash rather than closing it.

Configurations

Only deployments that configure a static "memo" in the Tempo method_config are affected. Deployments using the default per-challenge attribution memo are not: that path binds each settled transfer to the challenge under verification and is single-use by construction.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Authentication Bypass by Capture-replay in ZenHive mpp allows an unauthenticated remote client to obtain paid resources by resubmitting one settled on-chain transfer.

MPP.Methods.EVM.verify/2 accepts a transaction-hash credential and matches a transfer purely on token, to and amount (ERC-20) or to and value (native). It binds the proof neither to the challenge being verified nor to any record of prior use, and the generic MPP.Plug dedup store keys on challenge.id, which is regenerated for every 402 response. On a static-price route, a single historical transfer matching the charge therefore satisfies an unbounded number of later charges, including transfers an attacker can read off a public block explorer.

This issue affects mpp: from 0.3.0 before 0.6.3.

Workarounds

Price each challenge uniquely (per-challenge or single-use amounts) so that a historical transfer cannot match a later charge, and keep challenge expiry short to narrow the window in which any given transfer stays useful. Deployments that can use the Tempo method for on-chain payments get per-challenge attribution binding instead.

Summary

Allocation of Resources Without Limits or Throttling in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet through concurrent sponsored payments, denying service to legitimate payers once it is empty.

MPP.Methods.Tempo.FeePayerPolicy enforces its ceilings (max_gas, max_fee_per_gas, max_priority_fee_per_gas, the worst-case gas_limit * max_fee_per_gas <= max_total_fee budget cap, and a validity window) against one transaction at a time, and nothing accounts for exposure across concurrent requests. reserve_hash_atomic/2 is keyed on the transaction hash, so it prevents duplicate broadcast of the same signed transaction but not N distinct sponsored transactions carrying distinct expiring nonces. Committed sponsor exposure is therefore N times max_total_fee, bounded by nothing in the library, and the default 900 second validity window lets co-signed transactions stay broadcastable and uncounted for that entire period.

This issue affects mpp: from 0.2.0 before 0.12.0.

Workarounds

Disable Tempo fee sponsorship by setting "fee_payer" => false (the default), so the client pays its own gas and the sponsor wallet is never committed. Where sponsorship must stay enabled, lowering max_total_fee and max_validity_window_seconds reduces the exposure each concurrent request can commit and how long it stays outstanding, without bounding the aggregate.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Authentication Bypass by Capture-replay in ZenHive mpp allows an unauthenticated third party to obtain paid resources by replaying a transfer settled by an unrelated payer.

MPP.Methods.Tempo normally binds a settled TIP-20 TransferWithMemo to the specific challenge under verification through an attribution nonce carried in the memo. When a static "memo" is configured in method_config, check_matched_memo_binding/3 returns the match unconditionally and that binding is skipped, leaving only token, recipient, amount and the static memo value to match on. The static memo is echoed in every unauthenticated 402 response and Tempo transfers are public, so an attacker can take any matching transfer paid by a legitimate customer, request a fresh challenge for the same route, and present that transaction hash as a type="hash" credential. The hash path performs no sender or signature check tying the presenter to the wallet that broadcast the transfer.

This issue affects mpp: from 0.6.1 before 0.6.4.

Workarounds

Remove the static "memo" from the Tempo method_config so verification falls back to the default per-challenge attribution binding, which ties each settled transfer to the challenge being verified. Where a static memo must be kept, configure a dedup store (for example MPP.Tempo.ConCacheStore) with a TTL at least as long as the challenge expiry, which reduces unlimited replay to a race on the transaction hash rather than closing it.

Configurations

Only deployments that configure a static "memo" in the Tempo method_config are affected. Deployments using the default per-challenge attribution memo are not: that path binds each settled transfer to the challenge under verification and is single-use by construction.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Authentication Bypass by Capture-replay in ZenHive mpp allows an unauthenticated remote client to obtain paid resources by resubmitting one settled on-chain transfer.

MPP.Methods.EVM.verify/2 accepts a transaction-hash credential and matches a transfer purely on token, to and amount (ERC-20) or to and value (native). It binds the proof neither to the challenge being verified nor to any record of prior use, and the generic MPP.Plug dedup store keys on challenge.id, which is regenerated for every 402 response. On a static-price route, a single historical transfer matching the charge therefore satisfies an unbounded number of later charges, including transfers an attacker can read off a public block explorer.

This issue affects mpp: from 0.3.0 before 0.6.3.

Workarounds

Price each challenge uniquely (per-challenge or single-use amounts) so that a historical transfer cannot match a later charge, and keep challenge expiry short to narrow the window in which any given transfer stays useful. Deployments that can use the Tempo method for on-chain payments get per-challenge attribution binding instead.

Summary

Allocation of Resources Without Limits or Throttling in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet through concurrent sponsored payments, denying service to legitimate payers once it is empty.

MPP.Methods.Tempo.FeePayerPolicy enforces its ceilings (max_gas, max_fee_per_gas, max_priority_fee_per_gas, the worst-case gas_limit * max_fee_per_gas <= max_total_fee budget cap, and a validity window) against one transaction at a time, and nothing accounts for exposure across concurrent requests. reserve_hash_atomic/2 is keyed on the transaction hash, so it prevents duplicate broadcast of the same signed transaction but not N distinct sponsored transactions carrying distinct expiring nonces. Committed sponsor exposure is therefore N times max_total_fee, bounded by nothing in the library, and the default 900 second validity window lets co-signed transactions stay broadcastable and uncounted for that entire period.

This issue affects mpp: from 0.2.0 before 0.12.0.

Workarounds

Disable Tempo fee sponsorship by setting "fee_payer" => false (the default), so the client pays its own gas and the sponsor wallet is never committed. Where sponsorship must stay enabled, lowering max_total_fee and max_validity_window_seconds reduces the exposure each concurrent request can commit and how long it stays outstanding, without bounding the aggregate.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Time-of-check Time-of-use (TOCTOU) Race Condition in ZenHive mpp allows an unauthenticated remote client to redeem one confirmed on-chain payment for multiple paid-resource accesses.

The type="hash" credential path in MPP.Methods.Tempo.verify/2 guards against replay with a non-atomic check-then-mark sequence: check_hash_unused/2 reads the dedup store, an eth_getTransactionReceipt round trip verifies the payment on chain, and only then does mark_hash_used/2 write the mark. Concurrent requests carrying the same settled payment hash all pass the read before any of them writes, so each is issued a receipt. The store's atomic check_and_mark/2 primitive is available and used by the type="transaction" path, but the hash path calls plain get and put even when the configured store implements it. Exploitation requires a dedup store to be configured; the default nil store is stateless and documented as offering no replay protection at all.

This issue affects mpp: from 0.2.0 before 0.6.1.

Configurations

The race is only reachable when MPP.Methods.Tempo is configured with a dedup store ("store" in method_config). The default is nil, which runs the library statelessly and provides no application-level replay protection at all, a documented property rather than part of this issue.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Authentication Bypass by Capture-replay in ZenHive mpp allows an unauthenticated remote client to obtain paid resources by resubmitting one settled on-chain transfer.

MPP.Methods.EVM.verify/2 accepts a transaction-hash credential and matches a transfer purely on token, to and amount (ERC-20) or to and value (native). It binds the proof neither to the challenge being verified nor to any record of prior use, and the generic MPP.Plug dedup store keys on challenge.id, which is regenerated for every 402 response. On a static-price route, a single historical transfer matching the charge therefore satisfies an unbounded number of later charges, including transfers an attacker can read off a public block explorer.

This issue affects mpp: from 0.3.0 before 0.6.3.

Workarounds

Price each challenge uniquely (per-challenge or single-use amounts) so that a historical transfer cannot match a later charge, and keep challenge expiry short to narrow the window in which any given transfer stays useful. Deployments that can use the Tempo method for on-chain payments get per-challenge attribution binding instead.

Summary

Allocation of Resources Without Limits or Throttling in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet through concurrent sponsored payments, denying service to legitimate payers once it is empty.

MPP.Methods.Tempo.FeePayerPolicy enforces its ceilings (max_gas, max_fee_per_gas, max_priority_fee_per_gas, the worst-case gas_limit * max_fee_per_gas <= max_total_fee budget cap, and a validity window) against one transaction at a time, and nothing accounts for exposure across concurrent requests. reserve_hash_atomic/2 is keyed on the transaction hash, so it prevents duplicate broadcast of the same signed transaction but not N distinct sponsored transactions carrying distinct expiring nonces. Committed sponsor exposure is therefore N times max_total_fee, bounded by nothing in the library, and the default 900 second validity window lets co-signed transactions stay broadcastable and uncounted for that entire period.

This issue affects mpp: from 0.2.0 before 0.12.0.

Workarounds

Disable Tempo fee sponsorship by setting "fee_payer" => false (the default), so the client pays its own gas and the sponsor wallet is never committed. Where sponsorship must stay enabled, lowering max_total_fee and max_validity_window_seconds reduces the exposure each concurrent request can commit and how long it stays outstanding, without bounding the aggregate.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Time-of-check Time-of-use (TOCTOU) Race Condition in ZenHive mpp allows an unauthenticated remote client to redeem one confirmed on-chain payment for multiple paid-resource accesses.

The type="hash" credential path in MPP.Methods.Tempo.verify/2 guards against replay with a non-atomic check-then-mark sequence: check_hash_unused/2 reads the dedup store, an eth_getTransactionReceipt round trip verifies the payment on chain, and only then does mark_hash_used/2 write the mark. Concurrent requests carrying the same settled payment hash all pass the read before any of them writes, so each is issued a receipt. The store's atomic check_and_mark/2 primitive is available and used by the type="transaction" path, but the hash path calls plain get and put even when the configured store implements it. Exploitation requires a dedup store to be configured; the default nil store is stateless and documented as offering no replay protection at all.

This issue affects mpp: from 0.2.0 before 0.6.1.

Configurations

The race is only reachable when MPP.Methods.Tempo is configured with a dedup store ("store" in method_config). The default is nil, which runs the library statelessly and provides no application-level replay protection at all, a documented property rather than part of this issue.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet, resulting in denial of service for legitimate clients.

When the mpp Elixir library is configured as fee payer (fee_payer: true), the MPP.Methods.Tempo payment method co-signs and broadcasts a client-supplied EVM transaction without first validating that the client-supplied gas_limit is sufficient to complete the intended call. A malicious client can submit a signed transferWithMemo transaction with gas_limit deliberately set just below the amount required for successful execution. The server co-signs the transaction and broadcasts it via rpc_broadcast_sync. The transaction runs out of gas during EVM execution and reverts, but the fee-payer wallet is still charged for the burned gas while the client pays nothing and receives no resource. Repeated requests from one or more malicious clients drain the fee-payer wallet at near-zero cost to the attacker, ultimately preventing the server from sponsoring gas for legitimate payment requests.

The wait_for_confirmation = false (optimistic) path is also affected: it invokes simulate_payment_call via eth_call, but that simulation omits the gas parameter and therefore does not catch out-of-gas conditions.

This issue affects mpp: from 0.2.0 before 0.6.0.

Configurations

The vulnerable code path is only reachable when the MPP.Methods.Tempo method is configured with fee_payer: true (server-side gas sponsorship). Default deployments with fee_payer: false are not affected, since the client pays for gas out of its own wallet.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per payment by a large multiplier, degrading the sponsor's operating margin.

When the mpp Elixir library is configured as fee payer (fee_payer: true), MPP.Tempo.Transaction.cosign_fee_payer/3 re-signs the client-supplied base fields of the 0x76 AASigned envelope verbatim, including the EIP-2930 access list, without validating its length or contents. EIP-2930 access list entries incur intrinsic gas (~2,400 gas per address, plus 1,900 gas per storage key) charged before any opcode executes, regardless of whether the listed addresses are ever touched. A malicious client submits a valid transferWithMemo call alongside a large number of fabricated access-list entries. The server co-signs and broadcasts the transaction. The intended transfer executes normally, but the fee-payer wallet pays a large multiple of the expected gas cost with no corresponding on-chain work.

At the maintainer's default of 137 access-list entries (fitting within Bandit's 10,000-byte per-header-field limit) and 100 Gwei max_fee_per_gas, per-payment gas cost rises from ~51,287 to ~380,087 gas, a 7.4x multiplier. Sustained abuse destroys the sponsor's operating margin on low-cost payments and, over time, drains the fee-payer wallet.

This issue affects mpp: from 0.2.0 before 0.6.0.

Configurations

The vulnerable code path is only reachable when the MPP.Methods.Tempo method is configured with fee_payer: true (server-side gas sponsorship). Default deployments with fee_payer: false are not affected, since the client pays for gas out of its own wallet.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet in a single request by naming an arbitrarily high gas price.

When the mpp Elixir library is configured as fee payer (fee_payer: true), MPP.Tempo.Transaction.cosign_fee_payer/3 re-signs the client-supplied base fields of the 0x76 AASigned envelope verbatim, including max_fee_per_gas and max_priority_fee_per_gas, without validating that they are within reasonable bounds. A malicious client embeds arbitrarily large values for these fields in the signed envelope. The server co-signs and broadcasts the transaction. The effective_gas_price billed against the fee-payer wallet is derived from the attacker-supplied ceilings, so the server pays those inflated per-gas rates out of its own wallet. A single crafted request can drain the wallet entirely, after which the server can no longer sponsor gas for legitimate payment requests.

This issue affects mpp: from 0.2.0 before 0.6.0.

Configurations

The vulnerable code path is only reachable when the MPP.Methods.Tempo method is configured with fee_payer: true (server-side gas sponsorship). Default deployments with fee_payer: false are not affected, since the client pays for gas out of its own wallet.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Authentication Bypass by Capture-replay in ZenHive mpp allows an unauthenticated remote client to obtain paid resources by resubmitting one settled on-chain transfer.

MPP.Methods.EVM.verify/2 accepts a transaction-hash credential and matches a transfer purely on token, to and amount (ERC-20) or to and value (native). It binds the proof neither to the challenge being verified nor to any record of prior use, and the generic MPP.Plug dedup store keys on challenge.id, which is regenerated for every 402 response. On a static-price route, a single historical transfer matching the charge therefore satisfies an unbounded number of later charges, including transfers an attacker can read off a public block explorer.

This issue affects mpp: from 0.3.0 before 0.6.3.

Workarounds

Price each challenge uniquely (per-challenge or single-use amounts) so that a historical transfer cannot match a later charge, and keep challenge expiry short to narrow the window in which any given transfer stays useful. Deployments that can use the Tempo method for on-chain payments get per-challenge attribution binding instead.

Summary

Allocation of Resources Without Limits or Throttling in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet through concurrent sponsored payments, denying service to legitimate payers once it is empty.

MPP.Methods.Tempo.FeePayerPolicy enforces its ceilings (max_gas, max_fee_per_gas, max_priority_fee_per_gas, the worst-case gas_limit * max_fee_per_gas <= max_total_fee budget cap, and a validity window) against one transaction at a time, and nothing accounts for exposure across concurrent requests. reserve_hash_atomic/2 is keyed on the transaction hash, so it prevents duplicate broadcast of the same signed transaction but not N distinct sponsored transactions carrying distinct expiring nonces. Committed sponsor exposure is therefore N times max_total_fee, bounded by nothing in the library, and the default 900 second validity window lets co-signed transactions stay broadcastable and uncounted for that entire period.

This issue affects mpp: from 0.2.0 before 0.12.0.

Workarounds

Disable Tempo fee sponsorship by setting "fee_payer" => false (the default), so the client pays its own gas and the sponsor wallet is never committed. Where sponsorship must stay enabled, lowering max_total_fee and max_validity_window_seconds reduces the exposure each concurrent request can commit and how long it stays outstanding, without bounding the aggregate.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Time-of-check Time-of-use (TOCTOU) Race Condition in ZenHive mpp allows an unauthenticated remote client to redeem one confirmed on-chain payment for multiple paid-resource accesses.

The type="hash" credential path in MPP.Methods.Tempo.verify/2 guards against replay with a non-atomic check-then-mark sequence: check_hash_unused/2 reads the dedup store, an eth_getTransactionReceipt round trip verifies the payment on chain, and only then does mark_hash_used/2 write the mark. Concurrent requests carrying the same settled payment hash all pass the read before any of them writes, so each is issued a receipt. The store's atomic check_and_mark/2 primitive is available and used by the type="transaction" path, but the hash path calls plain get and put even when the configured store implements it. Exploitation requires a dedup store to be configured; the default nil store is stateless and documented as offering no replay protection at all.

This issue affects mpp: from 0.2.0 before 0.6.1.

Configurations

The race is only reachable when MPP.Methods.Tempo is configured with a dedup store ("store" in method_config). The default is nil, which runs the library statelessly and provides no application-level replay protection at all, a documented property rather than part of this issue.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet, resulting in denial of service for legitimate clients.

When the mpp Elixir library is configured as fee payer (fee_payer: true), the MPP.Methods.Tempo payment method co-signs and broadcasts a client-supplied EVM transaction without first validating that the client-supplied gas_limit is sufficient to complete the intended call. A malicious client can submit a signed transferWithMemo transaction with gas_limit deliberately set just below the amount required for successful execution. The server co-signs the transaction and broadcasts it via rpc_broadcast_sync. The transaction runs out of gas during EVM execution and reverts, but the fee-payer wallet is still charged for the burned gas while the client pays nothing and receives no resource. Repeated requests from one or more malicious clients drain the fee-payer wallet at near-zero cost to the attacker, ultimately preventing the server from sponsoring gas for legitimate payment requests.

The wait_for_confirmation = false (optimistic) path is also affected: it invokes simulate_payment_call via eth_call, but that simulation omits the gas parameter and therefore does not catch out-of-gas conditions.

This issue affects mpp: from 0.2.0 before 0.6.0.

Configurations

The vulnerable code path is only reachable when the MPP.Methods.Tempo method is configured with fee_payer: true (server-side gas sponsorship). Default deployments with fee_payer: false are not affected, since the client pays for gas out of its own wallet.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per payment by a large multiplier, degrading the sponsor's operating margin.

When the mpp Elixir library is configured as fee payer (fee_payer: true), MPP.Tempo.Transaction.cosign_fee_payer/3 re-signs the client-supplied base fields of the 0x76 AASigned envelope verbatim, including the EIP-2930 access list, without validating its length or contents. EIP-2930 access list entries incur intrinsic gas (~2,400 gas per address, plus 1,900 gas per storage key) charged before any opcode executes, regardless of whether the listed addresses are ever touched. A malicious client submits a valid transferWithMemo call alongside a large number of fabricated access-list entries. The server co-signs and broadcasts the transaction. The intended transfer executes normally, but the fee-payer wallet pays a large multiple of the expected gas cost with no corresponding on-chain work.

At the maintainer's default of 137 access-list entries (fitting within Bandit's 10,000-byte per-header-field limit) and 100 Gwei max_fee_per_gas, per-payment gas cost rises from ~51,287 to ~380,087 gas, a 7.4x multiplier. Sustained abuse destroys the sponsor's operating margin on low-cost payments and, over time, drains the fee-payer wallet.

This issue affects mpp: from 0.2.0 before 0.6.0.

Configurations

The vulnerable code path is only reachable when the MPP.Methods.Tempo method is configured with fee_payer: true (server-side gas sponsorship). Default deployments with fee_payer: false are not affected, since the client pays for gas out of its own wallet.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet in a single request by naming an arbitrarily high gas price.

When the mpp Elixir library is configured as fee payer (fee_payer: true), MPP.Tempo.Transaction.cosign_fee_payer/3 re-signs the client-supplied base fields of the 0x76 AASigned envelope verbatim, including max_fee_per_gas and max_priority_fee_per_gas, without validating that they are within reasonable bounds. A malicious client embeds arbitrarily large values for these fields in the signed envelope. The server co-signs and broadcasts the transaction. The effective_gas_price billed against the fee-payer wallet is derived from the attacker-supplied ceilings, so the server pays those inflated per-gas rates out of its own wallet. A single crafted request can drain the wallet entirely, after which the server can no longer sponsor gas for legitimate payment requests.

This issue affects mpp: from 0.2.0 before 0.6.0.

Configurations

The vulnerable code path is only reachable when the MPP.Methods.Tempo method is configured with fee_payer: true (server-side gas sponsorship). Default deployments with fee_payer: false are not affected, since the client pays for gas out of its own wallet.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Authentication Bypass by Capture-replay in ZenHive mpp allows an unauthenticated remote client to obtain paid resources by resubmitting one settled on-chain transfer.

MPP.Methods.EVM.verify/2 accepts a transaction-hash credential and matches a transfer purely on token, to and amount (ERC-20) or to and value (native). It binds the proof neither to the challenge being verified nor to any record of prior use, and the generic MPP.Plug dedup store keys on challenge.id, which is regenerated for every 402 response. On a static-price route, a single historical transfer matching the charge therefore satisfies an unbounded number of later charges, including transfers an attacker can read off a public block explorer.

This issue affects mpp: from 0.3.0 before 0.6.3.

Workarounds

Price each challenge uniquely (per-challenge or single-use amounts) so that a historical transfer cannot match a later charge, and keep challenge expiry short to narrow the window in which any given transfer stays useful. Deployments that can use the Tempo method for on-chain payments get per-challenge attribution binding instead.

Summary

Allocation of Resources Without Limits or Throttling in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet through concurrent sponsored payments, denying service to legitimate payers once it is empty.

MPP.Methods.Tempo.FeePayerPolicy enforces its ceilings (max_gas, max_fee_per_gas, max_priority_fee_per_gas, the worst-case gas_limit * max_fee_per_gas <= max_total_fee budget cap, and a validity window) against one transaction at a time, and nothing accounts for exposure across concurrent requests. reserve_hash_atomic/2 is keyed on the transaction hash, so it prevents duplicate broadcast of the same signed transaction but not N distinct sponsored transactions carrying distinct expiring nonces. Committed sponsor exposure is therefore N times max_total_fee, bounded by nothing in the library, and the default 900 second validity window lets co-signed transactions stay broadcastable and uncounted for that entire period.

This issue affects mpp: from 0.2.0 before 0.12.0.

Workarounds

Disable Tempo fee sponsorship by setting "fee_payer" => false (the default), so the client pays its own gas and the sponsor wallet is never committed. Where sponsorship must stay enabled, lowering max_total_fee and max_validity_window_seconds reduces the exposure each concurrent request can commit and how long it stays outstanding, without bounding the aggregate.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Time-of-check Time-of-use (TOCTOU) Race Condition in ZenHive mpp allows an unauthenticated remote client to redeem one confirmed on-chain payment for multiple paid-resource accesses.

The type="hash" credential path in MPP.Methods.Tempo.verify/2 guards against replay with a non-atomic check-then-mark sequence: check_hash_unused/2 reads the dedup store, an eth_getTransactionReceipt round trip verifies the payment on chain, and only then does mark_hash_used/2 write the mark. Concurrent requests carrying the same settled payment hash all pass the read before any of them writes, so each is issued a receipt. The store's atomic check_and_mark/2 primitive is available and used by the type="transaction" path, but the hash path calls plain get and put even when the configured store implements it. Exploitation requires a dedup store to be configured; the default nil store is stateless and documented as offering no replay protection at all.

This issue affects mpp: from 0.2.0 before 0.6.1.

Configurations

The race is only reachable when MPP.Methods.Tempo is configured with a dedup store ("store" in method_config). The default is nil, which runs the library statelessly and provides no application-level replay protection at all, a documented property rather than part of this issue.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet, resulting in denial of service for legitimate clients.

When the mpp Elixir library is configured as fee payer (fee_payer: true), the MPP.Methods.Tempo payment method co-signs and broadcasts a client-supplied EVM transaction without first validating that the client-supplied gas_limit is sufficient to complete the intended call. A malicious client can submit a signed transferWithMemo transaction with gas_limit deliberately set just below the amount required for successful execution. The server co-signs the transaction and broadcasts it via rpc_broadcast_sync. The transaction runs out of gas during EVM execution and reverts, but the fee-payer wallet is still charged for the burned gas while the client pays nothing and receives no resource. Repeated requests from one or more malicious clients drain the fee-payer wallet at near-zero cost to the attacker, ultimately preventing the server from sponsoring gas for legitimate payment requests.

The wait_for_confirmation = false (optimistic) path is also affected: it invokes simulate_payment_call via eth_call, but that simulation omits the gas parameter and therefore does not catch out-of-gas conditions.

This issue affects mpp: from 0.2.0 before 0.6.0.

Configurations

The vulnerable code path is only reachable when the MPP.Methods.Tempo method is configured with fee_payer: true (server-side gas sponsorship). Default deployments with fee_payer: false are not affected, since the client pays for gas out of its own wallet.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per payment by a large multiplier, degrading the sponsor's operating margin.

When the mpp Elixir library is configured as fee payer (fee_payer: true), MPP.Tempo.Transaction.cosign_fee_payer/3 re-signs the client-supplied base fields of the 0x76 AASigned envelope verbatim, including the EIP-2930 access list, without validating its length or contents. EIP-2930 access list entries incur intrinsic gas (~2,400 gas per address, plus 1,900 gas per storage key) charged before any opcode executes, regardless of whether the listed addresses are ever touched. A malicious client submits a valid transferWithMemo call alongside a large number of fabricated access-list entries. The server co-signs and broadcasts the transaction. The intended transfer executes normally, but the fee-payer wallet pays a large multiple of the expected gas cost with no corresponding on-chain work.

At the maintainer's default of 137 access-list entries (fitting within Bandit's 10,000-byte per-header-field limit) and 100 Gwei max_fee_per_gas, per-payment gas cost rises from ~51,287 to ~380,087 gas, a 7.4x multiplier. Sustained abuse destroys the sponsor's operating margin on low-cost payments and, over time, drains the fee-payer wallet.

This issue affects mpp: from 0.2.0 before 0.6.0.

Configurations

The vulnerable code path is only reachable when the MPP.Methods.Tempo method is configured with fee_payer: true (server-side gas sponsorship). Default deployments with fee_payer: false are not affected, since the client pays for gas out of its own wallet.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet in a single request by naming an arbitrarily high gas price.

When the mpp Elixir library is configured as fee payer (fee_payer: true), MPP.Tempo.Transaction.cosign_fee_payer/3 re-signs the client-supplied base fields of the 0x76 AASigned envelope verbatim, including max_fee_per_gas and max_priority_fee_per_gas, without validating that they are within reasonable bounds. A malicious client embeds arbitrarily large values for these fields in the signed envelope. The server co-signs and broadcasts the transaction. The effective_gas_price billed against the fee-payer wallet is derived from the attacker-supplied ceilings, so the server pays those inflated per-gas rates out of its own wallet. A single crafted request can drain the wallet entirely, after which the server can no longer sponsor gas for legitimate payment requests.

This issue affects mpp: from 0.2.0 before 0.6.0.

Configurations

The vulnerable code path is only reachable when the MPP.Methods.Tempo method is configured with fee_payer: true (server-side gas sponsorship). Default deployments with fee_payer: false are not affected, since the client pays for gas out of its own wallet.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Authentication Bypass by Capture-replay in ZenHive mpp allows an unauthenticated remote client to obtain paid resources by resubmitting one settled on-chain transfer.

MPP.Methods.EVM.verify/2 accepts a transaction-hash credential and matches a transfer purely on token, to and amount (ERC-20) or to and value (native). It binds the proof neither to the challenge being verified nor to any record of prior use, and the generic MPP.Plug dedup store keys on challenge.id, which is regenerated for every 402 response. On a static-price route, a single historical transfer matching the charge therefore satisfies an unbounded number of later charges, including transfers an attacker can read off a public block explorer.

This issue affects mpp: from 0.3.0 before 0.6.3.

Workarounds

Price each challenge uniquely (per-challenge or single-use amounts) so that a historical transfer cannot match a later charge, and keep challenge expiry short to narrow the window in which any given transfer stays useful. Deployments that can use the Tempo method for on-chain payments get per-challenge attribution binding instead.

Summary

Allocation of Resources Without Limits or Throttling in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet through concurrent sponsored payments, denying service to legitimate payers once it is empty.

MPP.Methods.Tempo.FeePayerPolicy enforces its ceilings (max_gas, max_fee_per_gas, max_priority_fee_per_gas, the worst-case gas_limit * max_fee_per_gas <= max_total_fee budget cap, and a validity window) against one transaction at a time, and nothing accounts for exposure across concurrent requests. reserve_hash_atomic/2 is keyed on the transaction hash, so it prevents duplicate broadcast of the same signed transaction but not N distinct sponsored transactions carrying distinct expiring nonces. Committed sponsor exposure is therefore N times max_total_fee, bounded by nothing in the library, and the default 900 second validity window lets co-signed transactions stay broadcastable and uncounted for that entire period.

This issue affects mpp: from 0.2.0 before 0.12.0.

Workarounds

Disable Tempo fee sponsorship by setting "fee_payer" => false (the default), so the client pays its own gas and the sponsor wallet is never committed. Where sponsorship must stay enabled, lowering max_total_fee and max_validity_window_seconds reduces the exposure each concurrent request can commit and how long it stays outstanding, without bounding the aggregate.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Time-of-check Time-of-use (TOCTOU) Race Condition in ZenHive mpp allows an unauthenticated remote client to redeem one confirmed on-chain payment for multiple paid-resource accesses.

The type="hash" credential path in MPP.Methods.Tempo.verify/2 guards against replay with a non-atomic check-then-mark sequence: check_hash_unused/2 reads the dedup store, an eth_getTransactionReceipt round trip verifies the payment on chain, and only then does mark_hash_used/2 write the mark. Concurrent requests carrying the same settled payment hash all pass the read before any of them writes, so each is issued a receipt. The store's atomic check_and_mark/2 primitive is available and used by the type="transaction" path, but the hash path calls plain get and put even when the configured store implements it. Exploitation requires a dedup store to be configured; the default nil store is stateless and documented as offering no replay protection at all.

This issue affects mpp: from 0.2.0 before 0.6.1.

Configurations

The race is only reachable when MPP.Methods.Tempo is configured with a dedup store ("store" in method_config). The default is nil, which runs the library statelessly and provides no application-level replay protection at all, a documented property rather than part of this issue.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet, resulting in denial of service for legitimate clients.

When the mpp Elixir library is configured as fee payer (fee_payer: true), the MPP.Methods.Tempo payment method co-signs and broadcasts a client-supplied EVM transaction without first validating that the client-supplied gas_limit is sufficient to complete the intended call. A malicious client can submit a signed transferWithMemo transaction with gas_limit deliberately set just below the amount required for successful execution. The server co-signs the transaction and broadcasts it via rpc_broadcast_sync. The transaction runs out of gas during EVM execution and reverts, but the fee-payer wallet is still charged for the burned gas while the client pays nothing and receives no resource. Repeated requests from one or more malicious clients drain the fee-payer wallet at near-zero cost to the attacker, ultimately preventing the server from sponsoring gas for legitimate payment requests.

The wait_for_confirmation = false (optimistic) path is also affected: it invokes simulate_payment_call via eth_call, but that simulation omits the gas parameter and therefore does not catch out-of-gas conditions.

This issue affects mpp: from 0.2.0 before 0.6.0.

Configurations

The vulnerable code path is only reachable when the MPP.Methods.Tempo method is configured with fee_payer: true (server-side gas sponsorship). Default deployments with fee_payer: false are not affected, since the client pays for gas out of its own wallet.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per payment by a large multiplier, degrading the sponsor's operating margin.

When the mpp Elixir library is configured as fee payer (fee_payer: true), MPP.Tempo.Transaction.cosign_fee_payer/3 re-signs the client-supplied base fields of the 0x76 AASigned envelope verbatim, including the EIP-2930 access list, without validating its length or contents. EIP-2930 access list entries incur intrinsic gas (~2,400 gas per address, plus 1,900 gas per storage key) charged before any opcode executes, regardless of whether the listed addresses are ever touched. A malicious client submits a valid transferWithMemo call alongside a large number of fabricated access-list entries. The server co-signs and broadcasts the transaction. The intended transfer executes normally, but the fee-payer wallet pays a large multiple of the expected gas cost with no corresponding on-chain work.

At the maintainer's default of 137 access-list entries (fitting within Bandit's 10,000-byte per-header-field limit) and 100 Gwei max_fee_per_gas, per-payment gas cost rises from ~51,287 to ~380,087 gas, a 7.4x multiplier. Sustained abuse destroys the sponsor's operating margin on low-cost payments and, over time, drains the fee-payer wallet.

This issue affects mpp: from 0.2.0 before 0.6.0.

Configurations

The vulnerable code path is only reachable when the MPP.Methods.Tempo method is configured with fee_payer: true (server-side gas sponsorship). Default deployments with fee_payer: false are not affected, since the client pays for gas out of its own wallet.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet in a single request by naming an arbitrarily high gas price.

When the mpp Elixir library is configured as fee payer (fee_payer: true), MPP.Tempo.Transaction.cosign_fee_payer/3 re-signs the client-supplied base fields of the 0x76 AASigned envelope verbatim, including max_fee_per_gas and max_priority_fee_per_gas, without validating that they are within reasonable bounds. A malicious client embeds arbitrarily large values for these fields in the signed envelope. The server co-signs and broadcasts the transaction. The effective_gas_price billed against the fee-payer wallet is derived from the attacker-supplied ceilings, so the server pays those inflated per-gas rates out of its own wallet. A single crafted request can drain the wallet entirely, after which the server can no longer sponsor gas for legitimate payment requests.

This issue affects mpp: from 0.2.0 before 0.6.0.

Configurations

The vulnerable code path is only reachable when the MPP.Methods.Tempo method is configured with fee_payer: true (server-side gas sponsorship). Default deployments with fee_payer: false are not affected, since the client pays for gas out of its own wallet.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for EIP-7702 account delegations of the client's choosing.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but never reads its aa_authorization_list field. Every signed delegation in that list is charged as intrinsic gas before the payment call runs, so a client attaching delegations from throwaway authority keys makes the sponsor pay for them within the default gas_limit ceiling. At the reporter's default of seven entries the sponsored cost rises from about 46,575 gas to about 1,884,087 gas. Because each entry is applied as a persistent set-code delegation, a client can also upgrade its own accounts to delegated code at the sponsor's expense.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope padded with delegations either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per sponsored payment by a large multiplier and to have the sponsor pay for provisioning an access key on the client's own account.

When the server sponsors Tempo payments, MPP.Methods.Tempo.FeePayerPolicy.measure/3 in lib/mpp/methods/tempo/fee_payer_policy.ex bounds the gas fields, the fee budget, the validity window and the access list of the client-signed 0x76 envelope, but does not check whether the envelope carries the optional key_authorization field. A client can attach a fully signed key authorization, provisioning a new access key with token spending limits on its own account, alongside the normal payment call. The key and each limit entry are persistent storage writes billed as intrinsic gas to the sponsor, bounded only by the gas_limit ceiling. At the reporter's default of one key with three token limits the sponsored cost rises from about 46,587 gas to about 1,808,700 gas, and the client keeps a valid access key it paid nothing for.

This issue affects mpp: from 0.2.0 before 0.16.1.

Workarounds

Disable Tempo fee sponsorship by leaving "fee_payer" at its default of false and setting no fee_payer_url, so the client pays its own gas. Where sponsorship must stay enabled, lower the max_gas override in fee_payer_policy to just above what a legitimate sponsored payment needs (a TIP-20 transfer is roughly 50,000 gas), so an envelope carrying a key authorization either fails the policy or runs out of gas at a bounded cost. This bounds the inflation without closing it.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Allocation of Resources Without Limits or Throttling in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet through concurrent sponsored payments, denying service to legitimate payers once it is empty.

MPP.Methods.Tempo.FeePayerPolicy enforces its ceilings (max_gas, max_fee_per_gas, max_priority_fee_per_gas, the worst-case gas_limit * max_fee_per_gas <= max_total_fee budget cap, and a validity window) against one transaction at a time, and nothing accounts for exposure across concurrent requests. reserve_hash_atomic/2 is keyed on the transaction hash, so it prevents duplicate broadcast of the same signed transaction but not N distinct sponsored transactions carrying distinct expiring nonces. Committed sponsor exposure is therefore N times max_total_fee, bounded by nothing in the library, and the default 900 second validity window lets co-signed transactions stay broadcastable and uncounted for that entire period.

This issue affects mpp: from 0.2.0 before 0.12.0.

Workarounds

Disable Tempo fee sponsorship by setting "fee_payer" => false (the default), so the client pays its own gas and the sponsor wallet is never committed. Where sponsorship must stay enabled, lowering max_total_fee and max_validity_window_seconds reduces the exposure each concurrent request can commit and how long it stays outstanding, without bounding the aggregate.

Configurations

Only deployments that enable Tempo server-side fee sponsorship are affected, through "fee_payer" => true in method_config with either local co-signing (fee_payer_private_key) or hosted sponsorship (fee_payer_url). Sponsorship is disabled by default.

Summary

Time-of-check Time-of-use (TOCTOU) Race Condition in ZenHive mpp allows an unauthenticated remote client to redeem one confirmed on-chain payment for multiple paid-resource accesses.

The type="hash" credential path in MPP.Methods.Tempo.verify/2 guards against replay with a non-atomic check-then-mark sequence: check_hash_unused/2 reads the dedup store, an eth_getTransactionReceipt round trip verifies the payment on chain, and only then does mark_hash_used/2 write the mark. Concurrent requests carrying the same settled payment hash all pass the read before any of them writes, so each is issued a receipt. The store's atomic check_and_mark/2 primitive is available and used by the type="transaction" path, but the hash path calls plain get and put even when the configured store implements it. Exploitation requires a dedup store to be configured; the default nil store is stateless and documented as offering no replay protection at all.

This issue affects mpp: from 0.2.0 before 0.6.1.

Configurations

The race is only reachable when MPP.Methods.Tempo is configured with a dedup store ("store" in method_config). The default is nil, which runs the library statelessly and provides no application-level replay protection at all, a documented property rather than part of this issue.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to drain the fee-payer wallet, resulting in denial of service for legitimate clients.

When the mpp Elixir library is configured as fee payer (fee_payer: true), the MPP.Methods.Tempo payment method co-signs and broadcasts a client-supplied EVM transaction without first validating that the client-supplied gas_limit is sufficient to complete the intended call. A malicious client can submit a signed transferWithMemo transaction with gas_limit deliberately set just below the amount required for successful execution. The server co-signs the transaction and broadcasts it via rpc_broadcast_sync. The transaction runs out of gas during EVM execution and reverts, but the fee-payer wallet is still charged for the burned gas while the client pays nothing and receives no resource. Repeated requests from one or more malicious clients drain the fee-payer wallet at near-zero cost to the attacker, ultimately preventing the server from sponsoring gas for legitimate payment requests.

The wait_for_confirmation = false (optimistic) path is also affected: it invokes simulate_payment_call via eth_call, but that simulation omits the gas parameter and therefore does not catch out-of-gas conditions.

This issue affects mpp: from 0.2.0 before 0.6.0.

Configurations

The vulnerable code path is only reachable when the MPP.Methods.Tempo method is configured with fee_payer: true (server-side gas sponsorship). Default deployments with fee_payer: false are not affected, since the client pays for gas out of its own wallet.

Summary

Improper Validation of Specified Quantity in Input in ZenHive mpp allows an unauthenticated remote client to inflate the fee-payer's gas cost per payment by a large multiplier, degrading the sponsor's operating margin.

When the mpp Elixir library is configured as fee payer (fee_payer: true), MPP.Tempo.Transaction.cosign_fee_payer/3 re-signs the client-supplied base fields of the 0x76 AASigned envelope verbatim, including the EIP-2930 access list, without validating its length or contents. EIP-2930 access list entries incur intrinsic gas (~2,400 gas per address, plus 1,900 gas per storage key) charged before any opcode executes, regardless of whether the listed addresses are ever touched. A malicious client submits a valid transferWithMemo call alongside a large number of fabricated access-list entries. The server co-signs and broadcasts the transaction. The intended transfer executes normally, but the fee-payer wallet pays a large multiple of the expected gas cost with no corresponding on-chain work.

At the maintainer's default of 137 access-list entries (fitting within Bandit's 10,000-byte per-header-field limit) and 100 Gwei max_fee_per_gas, per-payment gas cost rises from ~51,287 to ~380,087 gas, a 7.4x multiplier. Sustained abuse destroys the sponsor's operating margin on low-cost payments and, over time, drains the fee-payer wallet.