OctoPrint

Impact

OctoPrint versions up until and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 contain a vulnerability that allows an attacker with the FILE_UPLOAD permission to exfiltrate files from the host that OctoPrint has read access to, by moving them into the upload folder where they then can be downloaded from. This vulnerability was already reported as GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 but the fix provided in OctoPrint 1.11.2 turned out to be incomplete.

The primary risk lies in the potential exfiltration of secrets stored inside OctoPrint's config, or further system files. By removing important runtime files, this could also be used to impact the availability of the host after an attempted server restart. Given that the attacker requires a user account with file upload permissions, the actual impact of this should however hopefully be minimal in most cases.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Details

OctoPrint's web application is implemented in Flask, but uploads are first intercepted by a custom upload handler built on Tornado that sits in front of it. The handler streams the upload to a temporary file on disk - so files larger than the available memory can be uploaded - and rewrites the request, adding internal form fields that tell Flask where to find that temporary file.

These fields are reserved and meant to be set only by the upload handler, never by the client. The previous fix from GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 stripped them from the request received from the client when they were sent as multipart form fields, yet they could still reach Flask through other channels: as plain query parameters, or - since the Tornado handler and Flask did not parse requests identically - smuggled in via several "parser differentials" that looked harmless to the handler while Flask still saw the injected fields. Any of these let an attacker make OctoPrint treat an arbitrary file on the host as a freshly uploaded one and move it into the upload folder.

The following endpoints in OctoPrint are affected:

• /api/files/{local|sdcard}
• /api/languages
• /plugin/backup/restore
• /plugin/pluginmanager/upload_file

Further upload endpoints in third party plugins might be affected too.

The fix rejects requests carrying any of the reserved fields, aligns the Tornado handler's request parsing with Flask's (Werkzeug) to avoid any differential parsing, and re-validates the request rewritten by Tornado before forwarding it to Flask.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Koh Jun Sheng and Jacopo Tediosi.

Timeline

2026-06-04: Report received 2026-06-04: Report acknowledged 2026-06-08: Report verified 2026-06-17: Fix ready for 1.11.x 2026-06-22: Fix ported to 2.0.0 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 are affected by a vulnerability that allows injection of arbitrary HTML and JavaScript into Suppressed Command notifications popups generated by the printer.

An attacker who successfully convinces a victim to print a specially crafted file could exploit this issue to disrupt ongoing prints, extract information (including sensitive configuration settings, if the targeted user has the necessary permissions for that), or perform other actions on behalf of the targeted user within the OctoPrint instance.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Workaround

OctoPrint administrators can mitigate the risk by disabling popups:

• for Action Command notifications, set OctoPrint Settings -> Serial Connection -> Behaviour -> Sanity Checking -> Display notifications for suppressed commands to Never show notifications

It is also strongly recommended to ensure that files being printed originate from trusted sources, and, whenever possible, are sliced with an application's own slicer.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Timeline

2026-03-18: Report received 2026-04-01: Report verified 2026-04-01: Fix ready for 2.0.0 2026-06-22: Fix backported to 1.11.x 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up until and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 contain a vulnerability that allows an attacker with the FILE_UPLOAD permission to exfiltrate files from the host that OctoPrint has read access to, by moving them into the upload folder where they then can be downloaded from. This vulnerability was already reported as GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 but the fix provided in OctoPrint 1.11.2 turned out to be incomplete.

The primary risk lies in the potential exfiltration of secrets stored inside OctoPrint's config, or further system files. By removing important runtime files, this could also be used to impact the availability of the host after an attempted server restart. Given that the attacker requires a user account with file upload permissions, the actual impact of this should however hopefully be minimal in most cases.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Details

OctoPrint's web application is implemented in Flask, but uploads are first intercepted by a custom upload handler built on Tornado that sits in front of it. The handler streams the upload to a temporary file on disk - so files larger than the available memory can be uploaded - and rewrites the request, adding internal form fields that tell Flask where to find that temporary file.

These fields are reserved and meant to be set only by the upload handler, never by the client. The previous fix from GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 stripped them from the request received from the client when they were sent as multipart form fields, yet they could still reach Flask through other channels: as plain query parameters, or - since the Tornado handler and Flask did not parse requests identically - smuggled in via several "parser differentials" that looked harmless to the handler while Flask still saw the injected fields. Any of these let an attacker make OctoPrint treat an arbitrary file on the host as a freshly uploaded one and move it into the upload folder.

The following endpoints in OctoPrint are affected:

• /api/files/{local|sdcard}
• /api/languages
• /plugin/backup/restore
• /plugin/pluginmanager/upload_file

Further upload endpoints in third party plugins might be affected too.

The fix rejects requests carrying any of the reserved fields, aligns the Tornado handler's request parsing with Flask's (Werkzeug) to avoid any differential parsing, and re-validates the request rewritten by Tornado before forwarding it to Flask.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Koh Jun Sheng and Jacopo Tediosi.

Timeline

2026-06-04: Report received 2026-06-04: Report acknowledged 2026-06-08: Report verified 2026-06-17: Fix ready for 1.11.x 2026-06-22: Fix ported to 2.0.0 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 are affected by a vulnerability that allows injection of arbitrary HTML and JavaScript into Suppressed Command notifications popups generated by the printer.

An attacker who successfully convinces a victim to print a specially crafted file could exploit this issue to disrupt ongoing prints, extract information (including sensitive configuration settings, if the targeted user has the necessary permissions for that), or perform other actions on behalf of the targeted user within the OctoPrint instance.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Workaround

OctoPrint administrators can mitigate the risk by disabling popups:

• for Action Command notifications, set OctoPrint Settings -> Serial Connection -> Behaviour -> Sanity Checking -> Display notifications for suppressed commands to Never show notifications

It is also strongly recommended to ensure that files being printed originate from trusted sources, and, whenever possible, are sliced with an application's own slicer.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Timeline

2026-03-18: Report received 2026-04-01: Report verified 2026-04-01: Fix ready for 2.0.0 2026-06-22: Fix backported to 1.11.x 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up until and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 contain a vulnerability that allows an attacker with the FILE_UPLOAD permission to exfiltrate files from the host that OctoPrint has read access to, by moving them into the upload folder where they then can be downloaded from. This vulnerability was already reported as GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 but the fix provided in OctoPrint 1.11.2 turned out to be incomplete.

The primary risk lies in the potential exfiltration of secrets stored inside OctoPrint's config, or further system files. By removing important runtime files, this could also be used to impact the availability of the host after an attempted server restart. Given that the attacker requires a user account with file upload permissions, the actual impact of this should however hopefully be minimal in most cases.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Details

OctoPrint's web application is implemented in Flask, but uploads are first intercepted by a custom upload handler built on Tornado that sits in front of it. The handler streams the upload to a temporary file on disk - so files larger than the available memory can be uploaded - and rewrites the request, adding internal form fields that tell Flask where to find that temporary file.

These fields are reserved and meant to be set only by the upload handler, never by the client. The previous fix from GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 stripped them from the request received from the client when they were sent as multipart form fields, yet they could still reach Flask through other channels: as plain query parameters, or - since the Tornado handler and Flask did not parse requests identically - smuggled in via several "parser differentials" that looked harmless to the handler while Flask still saw the injected fields. Any of these let an attacker make OctoPrint treat an arbitrary file on the host as a freshly uploaded one and move it into the upload folder.

The following endpoints in OctoPrint are affected:

• /api/files/{local|sdcard}
• /api/languages
• /plugin/backup/restore
• /plugin/pluginmanager/upload_file

Further upload endpoints in third party plugins might be affected too.

The fix rejects requests carrying any of the reserved fields, aligns the Tornado handler's request parsing with Flask's (Werkzeug) to avoid any differential parsing, and re-validates the request rewritten by Tornado before forwarding it to Flask.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Koh Jun Sheng and Jacopo Tediosi.

Timeline

2026-06-04: Report received 2026-06-04: Report acknowledged 2026-06-08: Report verified 2026-06-17: Fix ready for 1.11.x 2026-06-22: Fix ported to 2.0.0 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 are affected by a vulnerability that allows injection of arbitrary HTML and JavaScript into Suppressed Command notifications popups generated by the printer.

An attacker who successfully convinces a victim to print a specially crafted file could exploit this issue to disrupt ongoing prints, extract information (including sensitive configuration settings, if the targeted user has the necessary permissions for that), or perform other actions on behalf of the targeted user within the OctoPrint instance.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Workaround

OctoPrint administrators can mitigate the risk by disabling popups:

• for Action Command notifications, set OctoPrint Settings -> Serial Connection -> Behaviour -> Sanity Checking -> Display notifications for suppressed commands to Never show notifications

It is also strongly recommended to ensure that files being printed originate from trusted sources, and, whenever possible, are sliced with an application's own slicer.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Timeline

2026-03-18: Report received 2026-04-01: Report verified 2026-04-01: Fix ready for 2.0.0 2026-06-22: Fix backported to 1.11.x 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up until and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 contain a vulnerability that allows an attacker with the FILE_UPLOAD permission to exfiltrate files from the host that OctoPrint has read access to, by moving them into the upload folder where they then can be downloaded from. This vulnerability was already reported as GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 but the fix provided in OctoPrint 1.11.2 turned out to be incomplete.

The primary risk lies in the potential exfiltration of secrets stored inside OctoPrint's config, or further system files. By removing important runtime files, this could also be used to impact the availability of the host after an attempted server restart. Given that the attacker requires a user account with file upload permissions, the actual impact of this should however hopefully be minimal in most cases.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Details

OctoPrint's web application is implemented in Flask, but uploads are first intercepted by a custom upload handler built on Tornado that sits in front of it. The handler streams the upload to a temporary file on disk - so files larger than the available memory can be uploaded - and rewrites the request, adding internal form fields that tell Flask where to find that temporary file.

These fields are reserved and meant to be set only by the upload handler, never by the client. The previous fix from GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 stripped them from the request received from the client when they were sent as multipart form fields, yet they could still reach Flask through other channels: as plain query parameters, or - since the Tornado handler and Flask did not parse requests identically - smuggled in via several "parser differentials" that looked harmless to the handler while Flask still saw the injected fields. Any of these let an attacker make OctoPrint treat an arbitrary file on the host as a freshly uploaded one and move it into the upload folder.

The following endpoints in OctoPrint are affected:

• /api/files/{local|sdcard}
• /api/languages
• /plugin/backup/restore
• /plugin/pluginmanager/upload_file

Further upload endpoints in third party plugins might be affected too.

The fix rejects requests carrying any of the reserved fields, aligns the Tornado handler's request parsing with Flask's (Werkzeug) to avoid any differential parsing, and re-validates the request rewritten by Tornado before forwarding it to Flask.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Koh Jun Sheng and Jacopo Tediosi.

Timeline

2026-06-04: Report received 2026-06-04: Report acknowledged 2026-06-08: Report verified 2026-06-17: Fix ready for 1.11.x 2026-06-22: Fix ported to 2.0.0 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 are affected by a vulnerability that allows injection of arbitrary HTML and JavaScript into Suppressed Command notifications popups generated by the printer.

An attacker who successfully convinces a victim to print a specially crafted file could exploit this issue to disrupt ongoing prints, extract information (including sensitive configuration settings, if the targeted user has the necessary permissions for that), or perform other actions on behalf of the targeted user within the OctoPrint instance.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Workaround

OctoPrint administrators can mitigate the risk by disabling popups:

• for Action Command notifications, set OctoPrint Settings -> Serial Connection -> Behaviour -> Sanity Checking -> Display notifications for suppressed commands to Never show notifications

It is also strongly recommended to ensure that files being printed originate from trusted sources, and, whenever possible, are sliced with an application's own slicer.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Timeline

2026-03-18: Report received 2026-04-01: Report verified 2026-04-01: Fix ready for 2.0.0 2026-06-22: Fix backported to 1.11.x 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up until and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 contain a vulnerability that allows an attacker with the FILE_UPLOAD permission to exfiltrate files from the host that OctoPrint has read access to, by moving them into the upload folder where they then can be downloaded from. This vulnerability was already reported as GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 but the fix provided in OctoPrint 1.11.2 turned out to be incomplete.

The primary risk lies in the potential exfiltration of secrets stored inside OctoPrint's config, or further system files. By removing important runtime files, this could also be used to impact the availability of the host after an attempted server restart. Given that the attacker requires a user account with file upload permissions, the actual impact of this should however hopefully be minimal in most cases.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Details

OctoPrint's web application is implemented in Flask, but uploads are first intercepted by a custom upload handler built on Tornado that sits in front of it. The handler streams the upload to a temporary file on disk - so files larger than the available memory can be uploaded - and rewrites the request, adding internal form fields that tell Flask where to find that temporary file.

These fields are reserved and meant to be set only by the upload handler, never by the client. The previous fix from GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 stripped them from the request received from the client when they were sent as multipart form fields, yet they could still reach Flask through other channels: as plain query parameters, or - since the Tornado handler and Flask did not parse requests identically - smuggled in via several "parser differentials" that looked harmless to the handler while Flask still saw the injected fields. Any of these let an attacker make OctoPrint treat an arbitrary file on the host as a freshly uploaded one and move it into the upload folder.

The following endpoints in OctoPrint are affected:

• /api/files/{local|sdcard}
• /api/languages
• /plugin/backup/restore
• /plugin/pluginmanager/upload_file

Further upload endpoints in third party plugins might be affected too.

The fix rejects requests carrying any of the reserved fields, aligns the Tornado handler's request parsing with Flask's (Werkzeug) to avoid any differential parsing, and re-validates the request rewritten by Tornado before forwarding it to Flask.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Koh Jun Sheng and Jacopo Tediosi.

Timeline

2026-06-04: Report received 2026-06-04: Report acknowledged 2026-06-08: Report verified 2026-06-17: Fix ready for 1.11.x 2026-06-22: Fix ported to 2.0.0 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 are affected by a vulnerability that allows injection of arbitrary HTML and JavaScript into Suppressed Command notifications popups generated by the printer.

An attacker who successfully convinces a victim to print a specially crafted file could exploit this issue to disrupt ongoing prints, extract information (including sensitive configuration settings, if the targeted user has the necessary permissions for that), or perform other actions on behalf of the targeted user within the OctoPrint instance.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Workaround

OctoPrint administrators can mitigate the risk by disabling popups:

• for Action Command notifications, set OctoPrint Settings -> Serial Connection -> Behaviour -> Sanity Checking -> Display notifications for suppressed commands to Never show notifications

It is also strongly recommended to ensure that files being printed originate from trusted sources, and, whenever possible, are sliced with an application's own slicer.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Timeline

2026-03-18: Report received 2026-04-01: Report verified 2026-04-01: Fix ready for 2.0.0 2026-06-22: Fix backported to 1.11.x 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.5 are affected by a (theoretical) timing attack vulnerability that allows API key extraction over the network.

Due to using character based comparison that short-circuits on the first mismatched character during API key validation, rather than a cryptographical method with static runtime regardless of the point of mismatch, an attacker with network based access to an affected OctoPrint could extract API keys valid on the instance by measuring the response times of the denied access responses and guess an API key character by character.

Patches

The vulnerability will be patched in version 1.11.6.

Workaround

The likelihood of this attack actually working is highly dependent on the network's latency, noise and similar parameters. An actual proof of concept was not achieved so far. Still, as always administrators are advised to not expose their OctoPrint instance on hostile networks, especially not on the public Internet!

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Knox Liu.

Impact

OctoPrint versions up until and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 contain a vulnerability that allows an attacker with the FILE_UPLOAD permission to exfiltrate files from the host that OctoPrint has read access to, by moving them into the upload folder where they then can be downloaded from. This vulnerability was already reported as GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 but the fix provided in OctoPrint 1.11.2 turned out to be incomplete.

The primary risk lies in the potential exfiltration of secrets stored inside OctoPrint's config, or further system files. By removing important runtime files, this could also be used to impact the availability of the host after an attempted server restart. Given that the attacker requires a user account with file upload permissions, the actual impact of this should however hopefully be minimal in most cases.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Details

OctoPrint's web application is implemented in Flask, but uploads are first intercepted by a custom upload handler built on Tornado that sits in front of it. The handler streams the upload to a temporary file on disk - so files larger than the available memory can be uploaded - and rewrites the request, adding internal form fields that tell Flask where to find that temporary file.

These fields are reserved and meant to be set only by the upload handler, never by the client. The previous fix from GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 stripped them from the request received from the client when they were sent as multipart form fields, yet they could still reach Flask through other channels: as plain query parameters, or - since the Tornado handler and Flask did not parse requests identically - smuggled in via several "parser differentials" that looked harmless to the handler while Flask still saw the injected fields. Any of these let an attacker make OctoPrint treat an arbitrary file on the host as a freshly uploaded one and move it into the upload folder.

The following endpoints in OctoPrint are affected:

• /api/files/{local|sdcard}
• /api/languages
• /plugin/backup/restore
• /plugin/pluginmanager/upload_file

Further upload endpoints in third party plugins might be affected too.

The fix rejects requests carrying any of the reserved fields, aligns the Tornado handler's request parsing with Flask's (Werkzeug) to avoid any differential parsing, and re-validates the request rewritten by Tornado before forwarding it to Flask.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Koh Jun Sheng and Jacopo Tediosi.

Timeline

2026-06-04: Report received 2026-06-04: Report acknowledged 2026-06-08: Report verified 2026-06-17: Fix ready for 1.11.x 2026-06-22: Fix ported to 2.0.0 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 are affected by a vulnerability that allows injection of arbitrary HTML and JavaScript into Suppressed Command notifications popups generated by the printer.

An attacker who successfully convinces a victim to print a specially crafted file could exploit this issue to disrupt ongoing prints, extract information (including sensitive configuration settings, if the targeted user has the necessary permissions for that), or perform other actions on behalf of the targeted user within the OctoPrint instance.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Workaround

OctoPrint administrators can mitigate the risk by disabling popups:

• for Action Command notifications, set OctoPrint Settings -> Serial Connection -> Behaviour -> Sanity Checking -> Display notifications for suppressed commands to Never show notifications

It is also strongly recommended to ensure that files being printed originate from trusted sources, and, whenever possible, are sliced with an application's own slicer.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Timeline

2026-03-18: Report received 2026-04-01: Report verified 2026-04-01: Fix ready for 2.0.0 2026-06-22: Fix backported to 1.11.x 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.5 are affected by a (theoretical) timing attack vulnerability that allows API key extraction over the network.

Due to using character based comparison that short-circuits on the first mismatched character during API key validation, rather than a cryptographical method with static runtime regardless of the point of mismatch, an attacker with network based access to an affected OctoPrint could extract API keys valid on the instance by measuring the response times of the denied access responses and guess an API key character by character.

Patches

The vulnerability will be patched in version 1.11.6.

Workaround

The likelihood of this attack actually working is highly dependent on the network's latency, noise and similar parameters. An actual proof of concept was not achieved so far. Still, as always administrators are advised to not expose their OctoPrint instance on hostile networks, especially not on the public Internet!

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Knox Liu.

Impact

OctoPrint versions up until and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 contain a vulnerability that allows an attacker with the FILE_UPLOAD permission to exfiltrate files from the host that OctoPrint has read access to, by moving them into the upload folder where they then can be downloaded from. This vulnerability was already reported as GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 but the fix provided in OctoPrint 1.11.2 turned out to be incomplete.

The primary risk lies in the potential exfiltration of secrets stored inside OctoPrint's config, or further system files. By removing important runtime files, this could also be used to impact the availability of the host after an attempted server restart. Given that the attacker requires a user account with file upload permissions, the actual impact of this should however hopefully be minimal in most cases.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Details

OctoPrint's web application is implemented in Flask, but uploads are first intercepted by a custom upload handler built on Tornado that sits in front of it. The handler streams the upload to a temporary file on disk - so files larger than the available memory can be uploaded - and rewrites the request, adding internal form fields that tell Flask where to find that temporary file.

These fields are reserved and meant to be set only by the upload handler, never by the client. The previous fix from GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 stripped them from the request received from the client when they were sent as multipart form fields, yet they could still reach Flask through other channels: as plain query parameters, or - since the Tornado handler and Flask did not parse requests identically - smuggled in via several "parser differentials" that looked harmless to the handler while Flask still saw the injected fields. Any of these let an attacker make OctoPrint treat an arbitrary file on the host as a freshly uploaded one and move it into the upload folder.

The following endpoints in OctoPrint are affected:

• /api/files/{local|sdcard}
• /api/languages
• /plugin/backup/restore
• /plugin/pluginmanager/upload_file

Further upload endpoints in third party plugins might be affected too.

The fix rejects requests carrying any of the reserved fields, aligns the Tornado handler's request parsing with Flask's (Werkzeug) to avoid any differential parsing, and re-validates the request rewritten by Tornado before forwarding it to Flask.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Koh Jun Sheng and Jacopo Tediosi.

Timeline

2026-06-04: Report received 2026-06-04: Report acknowledged 2026-06-08: Report verified 2026-06-17: Fix ready for 1.11.x 2026-06-22: Fix ported to 2.0.0 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 are affected by a vulnerability that allows injection of arbitrary HTML and JavaScript into Suppressed Command notifications popups generated by the printer.

An attacker who successfully convinces a victim to print a specially crafted file could exploit this issue to disrupt ongoing prints, extract information (including sensitive configuration settings, if the targeted user has the necessary permissions for that), or perform other actions on behalf of the targeted user within the OctoPrint instance.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Workaround

OctoPrint administrators can mitigate the risk by disabling popups:

• for Action Command notifications, set OctoPrint Settings -> Serial Connection -> Behaviour -> Sanity Checking -> Display notifications for suppressed commands to Never show notifications

It is also strongly recommended to ensure that files being printed originate from trusted sources, and, whenever possible, are sliced with an application's own slicer.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Timeline

2026-03-18: Report received 2026-04-01: Report verified 2026-04-01: Fix ready for 2.0.0 2026-06-22: Fix backported to 1.11.x 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.5 are affected by a (theoretical) timing attack vulnerability that allows API key extraction over the network.

Due to using character based comparison that short-circuits on the first mismatched character during API key validation, rather than a cryptographical method with static runtime regardless of the point of mismatch, an attacker with network based access to an affected OctoPrint could extract API keys valid on the instance by measuring the response times of the denied access responses and guess an API key character by character.

Patches

The vulnerability will be patched in version 1.11.6.

Workaround

The likelihood of this attack actually working is highly dependent on the network's latency, noise and similar parameters. An actual proof of concept was not achieved so far. Still, as always administrators are advised to not expose their OctoPrint instance on hostile networks, especially not on the public Internet!

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Knox Liu.

Impact

OctoPrint versions up to and including 1.11.3 are affected by a vulnerability that allows injection of arbitrary HTML and JavaScript into Action Command notification and prompt popups generated by the printer.

An attacker who successfully convinces a victim to print a specially crafted file could exploit this issue to disrupt ongoing prints, extract information (including sensitive configuration settings, if the targeted user has the necessary permissions for that), or perform other actions on behalf of the targeted user within the OctoPrint instance.

Patches

The vulnerability will be patched in version 1.11.4.

Workaround

OctoPrint administrators can mitigate the risk by disabling popups:

• for Action Command notifications, uncheck OctoPrint Settings -> Printer Notifications -> Enable popups
• for Action Command prompts, set OctoPrint Settings -> Printer Dialogs -> Enable support -> Never

It is also strongly recommended to ensure that files being printed originate from trusted sources, and, whenever possible, are sliced with your own slicer.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Impact

OctoPrint versions up until and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 contain a vulnerability that allows an attacker with the FILE_UPLOAD permission to exfiltrate files from the host that OctoPrint has read access to, by moving them into the upload folder where they then can be downloaded from. This vulnerability was already reported as GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 but the fix provided in OctoPrint 1.11.2 turned out to be incomplete.

The primary risk lies in the potential exfiltration of secrets stored inside OctoPrint's config, or further system files. By removing important runtime files, this could also be used to impact the availability of the host after an attempted server restart. Given that the attacker requires a user account with file upload permissions, the actual impact of this should however hopefully be minimal in most cases.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Details

OctoPrint's web application is implemented in Flask, but uploads are first intercepted by a custom upload handler built on Tornado that sits in front of it. The handler streams the upload to a temporary file on disk - so files larger than the available memory can be uploaded - and rewrites the request, adding internal form fields that tell Flask where to find that temporary file.

These fields are reserved and meant to be set only by the upload handler, never by the client. The previous fix from GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 stripped them from the request received from the client when they were sent as multipart form fields, yet they could still reach Flask through other channels: as plain query parameters, or - since the Tornado handler and Flask did not parse requests identically - smuggled in via several "parser differentials" that looked harmless to the handler while Flask still saw the injected fields. Any of these let an attacker make OctoPrint treat an arbitrary file on the host as a freshly uploaded one and move it into the upload folder.

The following endpoints in OctoPrint are affected:

• /api/files/{local|sdcard}
• /api/languages
• /plugin/backup/restore
• /plugin/pluginmanager/upload_file

Further upload endpoints in third party plugins might be affected too.

The fix rejects requests carrying any of the reserved fields, aligns the Tornado handler's request parsing with Flask's (Werkzeug) to avoid any differential parsing, and re-validates the request rewritten by Tornado before forwarding it to Flask.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Koh Jun Sheng and Jacopo Tediosi.

Timeline

2026-06-04: Report received 2026-06-04: Report acknowledged 2026-06-08: Report verified 2026-06-17: Fix ready for 1.11.x 2026-06-22: Fix ported to 2.0.0 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 are affected by a vulnerability that allows injection of arbitrary HTML and JavaScript into Suppressed Command notifications popups generated by the printer.

An attacker who successfully convinces a victim to print a specially crafted file could exploit this issue to disrupt ongoing prints, extract information (including sensitive configuration settings, if the targeted user has the necessary permissions for that), or perform other actions on behalf of the targeted user within the OctoPrint instance.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Workaround

OctoPrint administrators can mitigate the risk by disabling popups:

• for Action Command notifications, set OctoPrint Settings -> Serial Connection -> Behaviour -> Sanity Checking -> Display notifications for suppressed commands to Never show notifications

It is also strongly recommended to ensure that files being printed originate from trusted sources, and, whenever possible, are sliced with an application's own slicer.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Timeline

2026-03-18: Report received 2026-04-01: Report verified 2026-04-01: Fix ready for 2.0.0 2026-06-22: Fix backported to 1.11.x 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.5 are affected by a (theoretical) timing attack vulnerability that allows API key extraction over the network.

Due to using character based comparison that short-circuits on the first mismatched character during API key validation, rather than a cryptographical method with static runtime regardless of the point of mismatch, an attacker with network based access to an affected OctoPrint could extract API keys valid on the instance by measuring the response times of the denied access responses and guess an API key character by character.

Patches

The vulnerability will be patched in version 1.11.6.

Workaround

The likelihood of this attack actually working is highly dependent on the network's latency, noise and similar parameters. An actual proof of concept was not achieved so far. Still, as always administrators are advised to not expose their OctoPrint instance on hostile networks, especially not on the public Internet!

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Knox Liu.

Impact

OctoPrint versions up to and including 1.11.3 are affected by a vulnerability that allows injection of arbitrary HTML and JavaScript into Action Command notification and prompt popups generated by the printer.

An attacker who successfully convinces a victim to print a specially crafted file could exploit this issue to disrupt ongoing prints, extract information (including sensitive configuration settings, if the targeted user has the necessary permissions for that), or perform other actions on behalf of the targeted user within the OctoPrint instance.

Patches

The vulnerability will be patched in version 1.11.4.

Workaround

OctoPrint administrators can mitigate the risk by disabling popups:

• for Action Command notifications, uncheck OctoPrint Settings -> Printer Notifications -> Enable popups
• for Action Command prompts, set OctoPrint Settings -> Printer Dialogs -> Enable support -> Never

It is also strongly recommended to ensure that files being printed originate from trusted sources, and, whenever possible, are sliced with your own slicer.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Impact

OctoPrint versions up until and including 1.11.2 contain a vulnerability that allows an authenticated attacker to upload a file under a specially crafted filename that will allow arbitrary command execution if said filename becomes included in a command defined in a system event handler and said event gets triggered.

If no event handlers executing system commands with uploaded filenames as parameters have been configured, this vulnerability does not have an impact.

Patches

The vulnerability will be patched in version 1.11.3.

Workaround

Until the patch has been applied, OctoPrint administrators who have event handlers configured that include any kind of filename based placeholders (i.e. {__filename}, {__filepath}, {filename}, {path}, etc -- refer to the events documentation for a full list) should disable those by setting their enabled property to False or unchecking the "Enabled" checkbox in the GUI based Event Manager.

Alternatively, OctoPrint administrators should set feature.enforceReallyUniversalFilenames to true in config.yaml and restart OctoPrint, then vet the existing uploads and make sure to delete any suspicious looking files (e.g. those that contain a ; in their name followed by a command).

As always, OctoPrint administrators are advised to not expose OctoPrint on hostile networks like the public internet, and to vet who has access to their instance.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by @prabhatverma47.

Impact

OctoPrint versions up until and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 contain a vulnerability that allows an attacker with the FILE_UPLOAD permission to exfiltrate files from the host that OctoPrint has read access to, by moving them into the upload folder where they then can be downloaded from. This vulnerability was already reported as GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 but the fix provided in OctoPrint 1.11.2 turned out to be incomplete.

The primary risk lies in the potential exfiltration of secrets stored inside OctoPrint's config, or further system files. By removing important runtime files, this could also be used to impact the availability of the host after an attempted server restart. Given that the attacker requires a user account with file upload permissions, the actual impact of this should however hopefully be minimal in most cases.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Details

OctoPrint's web application is implemented in Flask, but uploads are first intercepted by a custom upload handler built on Tornado that sits in front of it. The handler streams the upload to a temporary file on disk - so files larger than the available memory can be uploaded - and rewrites the request, adding internal form fields that tell Flask where to find that temporary file.

These fields are reserved and meant to be set only by the upload handler, never by the client. The previous fix from GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 stripped them from the request received from the client when they were sent as multipart form fields, yet they could still reach Flask through other channels: as plain query parameters, or - since the Tornado handler and Flask did not parse requests identically - smuggled in via several "parser differentials" that looked harmless to the handler while Flask still saw the injected fields. Any of these let an attacker make OctoPrint treat an arbitrary file on the host as a freshly uploaded one and move it into the upload folder.

The following endpoints in OctoPrint are affected:

• /api/files/{local|sdcard}
• /api/languages
• /plugin/backup/restore
• /plugin/pluginmanager/upload_file

Further upload endpoints in third party plugins might be affected too.

The fix rejects requests carrying any of the reserved fields, aligns the Tornado handler's request parsing with Flask's (Werkzeug) to avoid any differential parsing, and re-validates the request rewritten by Tornado before forwarding it to Flask.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Koh Jun Sheng and Jacopo Tediosi.

Timeline

2026-06-04: Report received 2026-06-04: Report acknowledged 2026-06-08: Report verified 2026-06-17: Fix ready for 1.11.x 2026-06-22: Fix ported to 2.0.0 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 are affected by a vulnerability that allows injection of arbitrary HTML and JavaScript into Suppressed Command notifications popups generated by the printer.

An attacker who successfully convinces a victim to print a specially crafted file could exploit this issue to disrupt ongoing prints, extract information (including sensitive configuration settings, if the targeted user has the necessary permissions for that), or perform other actions on behalf of the targeted user within the OctoPrint instance.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Workaround

OctoPrint administrators can mitigate the risk by disabling popups:

• for Action Command notifications, set OctoPrint Settings -> Serial Connection -> Behaviour -> Sanity Checking -> Display notifications for suppressed commands to Never show notifications

It is also strongly recommended to ensure that files being printed originate from trusted sources, and, whenever possible, are sliced with an application's own slicer.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Timeline

2026-03-18: Report received 2026-04-01: Report verified 2026-04-01: Fix ready for 2.0.0 2026-06-22: Fix backported to 1.11.x 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.5 are affected by a (theoretical) timing attack vulnerability that allows API key extraction over the network.

Due to using character based comparison that short-circuits on the first mismatched character during API key validation, rather than a cryptographical method with static runtime regardless of the point of mismatch, an attacker with network based access to an affected OctoPrint could extract API keys valid on the instance by measuring the response times of the denied access responses and guess an API key character by character.

Patches

The vulnerability will be patched in version 1.11.6.

Workaround

The likelihood of this attack actually working is highly dependent on the network's latency, noise and similar parameters. An actual proof of concept was not achieved so far. Still, as always administrators are advised to not expose their OctoPrint instance on hostile networks, especially not on the public Internet!

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Knox Liu.

Impact

OctoPrint versions up to and including 1.11.3 are affected by a vulnerability that allows injection of arbitrary HTML and JavaScript into Action Command notification and prompt popups generated by the printer.

An attacker who successfully convinces a victim to print a specially crafted file could exploit this issue to disrupt ongoing prints, extract information (including sensitive configuration settings, if the targeted user has the necessary permissions for that), or perform other actions on behalf of the targeted user within the OctoPrint instance.

Patches

The vulnerability will be patched in version 1.11.4.

Workaround

OctoPrint administrators can mitigate the risk by disabling popups:

• for Action Command notifications, uncheck OctoPrint Settings -> Printer Notifications -> Enable popups
• for Action Command prompts, set OctoPrint Settings -> Printer Dialogs -> Enable support -> Never

It is also strongly recommended to ensure that files being printed originate from trusted sources, and, whenever possible, are sliced with your own slicer.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Impact

OctoPrint versions up until and including 1.11.2 contain a vulnerability that allows an authenticated attacker to upload a file under a specially crafted filename that will allow arbitrary command execution if said filename becomes included in a command defined in a system event handler and said event gets triggered.

If no event handlers executing system commands with uploaded filenames as parameters have been configured, this vulnerability does not have an impact.

Patches

The vulnerability will be patched in version 1.11.3.

Workaround

Until the patch has been applied, OctoPrint administrators who have event handlers configured that include any kind of filename based placeholders (i.e. {__filename}, {__filepath}, {filename}, {path}, etc -- refer to the events documentation for a full list) should disable those by setting their enabled property to False or unchecking the "Enabled" checkbox in the GUI based Event Manager.

Alternatively, OctoPrint administrators should set feature.enforceReallyUniversalFilenames to true in config.yaml and restart OctoPrint, then vet the existing uploads and make sure to delete any suspicious looking files (e.g. those that contain a ; in their name followed by a command).

As always, OctoPrint administrators are advised to not expose OctoPrint on hostile networks like the public internet, and to vet who has access to their instance.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by @prabhatverma47.

Impact

OctoPrint versions up until and including 1.11.1 contain a vulnerability that allows any unauthenticated attacker to send a manipulated broken multipart/form-data request to OctoPrint and through that make the web server component become unresponsive. This could be used to effectively run a denial of service attack on the OctoPrint server.

Patches

The vulnerability has been patched in version 1.11.2.

Workaround

OctoPrint administrators are once more reminded to not make OctoPrint available on hostile networks (e.g. the internet), regardless of whether this vulnerability is patched or not.

Details

The issue can be triggered by a broken multipart/form-data request lacking an end boundary to any of OctoPrint's endpoints implemented through the octoprint.server.util.tornado.UploadStorageFallbackHandler request handler. The request handler will get stuck in an endless busy loop, looking for a part of the request that will never come. As Tornado is single-threaded, that will effectively block the whole web server.

The fix adds detection of invalid requests like that and ensures they are handled gracefully with an HTTP 400 Bad Request response.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Impact

OctoPrint versions up until and including 1.11.1 contain a vulnerability that allows an attacker with the FILE_UPLOAD permission to exfiltrate files from the host that OctoPrint has read access to, by moving them into the upload folder where they then can be downloaded from.

The primary risk lies in the potential exfiltration of secrets stored inside OctoPrint's config, or further system files. By removing important runtime files, this could also be used to impact the availability of the host. Given that the attacker requires a user account with file upload permissions, the actual impact of this should however hopefully be minimal in most cases.

Patches

The vulnerability has been patched in version 1.11.2.

Details

A specially crafted HTTP Request to an affected upload endpoint that contains some form inputs only supposed to be used internally can be used to make OctoPrint move a file that it thinks is a freshly uploaded temporary one into its upload folder.

The following endpoints in OctoPrint are affected:

• /api/files/{local|sdcard}
• /api/languages
• /plugin/backup/restore
• /plugin/pluginmanager/upload_file

Further upload endpoints in third party plugins might be affected too.

The fix removes any internal-only form inputs from incoming requests in the central file upload processor component.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi

Impact

OctoPrint versions up until and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 contain a vulnerability that allows an attacker with the FILE_UPLOAD permission to exfiltrate files from the host that OctoPrint has read access to, by moving them into the upload folder where they then can be downloaded from. This vulnerability was already reported as GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 but the fix provided in OctoPrint 1.11.2 turned out to be incomplete.

The primary risk lies in the potential exfiltration of secrets stored inside OctoPrint's config, or further system files. By removing important runtime files, this could also be used to impact the availability of the host after an attempted server restart. Given that the attacker requires a user account with file upload permissions, the actual impact of this should however hopefully be minimal in most cases.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Details

OctoPrint's web application is implemented in Flask, but uploads are first intercepted by a custom upload handler built on Tornado that sits in front of it. The handler streams the upload to a temporary file on disk - so files larger than the available memory can be uploaded - and rewrites the request, adding internal form fields that tell Flask where to find that temporary file.

These fields are reserved and meant to be set only by the upload handler, never by the client. The previous fix from GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 stripped them from the request received from the client when they were sent as multipart form fields, yet they could still reach Flask through other channels: as plain query parameters, or - since the Tornado handler and Flask did not parse requests identically - smuggled in via several "parser differentials" that looked harmless to the handler while Flask still saw the injected fields. Any of these let an attacker make OctoPrint treat an arbitrary file on the host as a freshly uploaded one and move it into the upload folder.

The following endpoints in OctoPrint are affected:

• /api/files/{local|sdcard}
• /api/languages
• /plugin/backup/restore
• /plugin/pluginmanager/upload_file

Further upload endpoints in third party plugins might be affected too.

The fix rejects requests carrying any of the reserved fields, aligns the Tornado handler's request parsing with Flask's (Werkzeug) to avoid any differential parsing, and re-validates the request rewritten by Tornado before forwarding it to Flask.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Koh Jun Sheng and Jacopo Tediosi.

Timeline

2026-06-04: Report received 2026-06-04: Report acknowledged 2026-06-08: Report verified 2026-06-17: Fix ready for 1.11.x 2026-06-22: Fix ported to 2.0.0 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 are affected by a vulnerability that allows injection of arbitrary HTML and JavaScript into Suppressed Command notifications popups generated by the printer.

An attacker who successfully convinces a victim to print a specially crafted file could exploit this issue to disrupt ongoing prints, extract information (including sensitive configuration settings, if the targeted user has the necessary permissions for that), or perform other actions on behalf of the targeted user within the OctoPrint instance.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Workaround

OctoPrint administrators can mitigate the risk by disabling popups:

• for Action Command notifications, set OctoPrint Settings -> Serial Connection -> Behaviour -> Sanity Checking -> Display notifications for suppressed commands to Never show notifications

It is also strongly recommended to ensure that files being printed originate from trusted sources, and, whenever possible, are sliced with an application's own slicer.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Timeline

2026-03-18: Report received 2026-04-01: Report verified 2026-04-01: Fix ready for 2.0.0 2026-06-22: Fix backported to 1.11.x 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.5 are affected by a (theoretical) timing attack vulnerability that allows API key extraction over the network.

Due to using character based comparison that short-circuits on the first mismatched character during API key validation, rather than a cryptographical method with static runtime regardless of the point of mismatch, an attacker with network based access to an affected OctoPrint could extract API keys valid on the instance by measuring the response times of the denied access responses and guess an API key character by character.

Patches

The vulnerability will be patched in version 1.11.6.

Workaround

The likelihood of this attack actually working is highly dependent on the network's latency, noise and similar parameters. An actual proof of concept was not achieved so far. Still, as always administrators are advised to not expose their OctoPrint instance on hostile networks, especially not on the public Internet!

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Knox Liu.

Impact

OctoPrint versions up to and including 1.11.3 are affected by a vulnerability that allows injection of arbitrary HTML and JavaScript into Action Command notification and prompt popups generated by the printer.

An attacker who successfully convinces a victim to print a specially crafted file could exploit this issue to disrupt ongoing prints, extract information (including sensitive configuration settings, if the targeted user has the necessary permissions for that), or perform other actions on behalf of the targeted user within the OctoPrint instance.

Patches

The vulnerability will be patched in version 1.11.4.

Workaround

OctoPrint administrators can mitigate the risk by disabling popups:

• for Action Command notifications, uncheck OctoPrint Settings -> Printer Notifications -> Enable popups
• for Action Command prompts, set OctoPrint Settings -> Printer Dialogs -> Enable support -> Never

It is also strongly recommended to ensure that files being printed originate from trusted sources, and, whenever possible, are sliced with your own slicer.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Impact

OctoPrint versions up until and including 1.11.2 contain a vulnerability that allows an authenticated attacker to upload a file under a specially crafted filename that will allow arbitrary command execution if said filename becomes included in a command defined in a system event handler and said event gets triggered.

If no event handlers executing system commands with uploaded filenames as parameters have been configured, this vulnerability does not have an impact.

Patches

The vulnerability will be patched in version 1.11.3.

Workaround

Until the patch has been applied, OctoPrint administrators who have event handlers configured that include any kind of filename based placeholders (i.e. {__filename}, {__filepath}, {filename}, {path}, etc -- refer to the events documentation for a full list) should disable those by setting their enabled property to False or unchecking the "Enabled" checkbox in the GUI based Event Manager.

Alternatively, OctoPrint administrators should set feature.enforceReallyUniversalFilenames to true in config.yaml and restart OctoPrint, then vet the existing uploads and make sure to delete any suspicious looking files (e.g. those that contain a ; in their name followed by a command).

As always, OctoPrint administrators are advised to not expose OctoPrint on hostile networks like the public internet, and to vet who has access to their instance.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by @prabhatverma47.

Impact

OctoPrint versions up until and including 1.11.1 contain a vulnerability that allows any unauthenticated attacker to send a manipulated broken multipart/form-data request to OctoPrint and through that make the web server component become unresponsive. This could be used to effectively run a denial of service attack on the OctoPrint server.

Patches

The vulnerability has been patched in version 1.11.2.

Workaround

OctoPrint administrators are once more reminded to not make OctoPrint available on hostile networks (e.g. the internet), regardless of whether this vulnerability is patched or not.

Details

The issue can be triggered by a broken multipart/form-data request lacking an end boundary to any of OctoPrint's endpoints implemented through the octoprint.server.util.tornado.UploadStorageFallbackHandler request handler. The request handler will get stuck in an endless busy loop, looking for a part of the request that will never come. As Tornado is single-threaded, that will effectively block the whole web server.

The fix adds detection of invalid requests like that and ensures they are handled gracefully with an HTTP 400 Bad Request response.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Impact

OctoPrint versions up until and including 1.11.1 contain a vulnerability that allows an attacker with the FILE_UPLOAD permission to exfiltrate files from the host that OctoPrint has read access to, by moving them into the upload folder where they then can be downloaded from.

The primary risk lies in the potential exfiltration of secrets stored inside OctoPrint's config, or further system files. By removing important runtime files, this could also be used to impact the availability of the host. Given that the attacker requires a user account with file upload permissions, the actual impact of this should however hopefully be minimal in most cases.

Patches

The vulnerability has been patched in version 1.11.2.

Details

A specially crafted HTTP Request to an affected upload endpoint that contains some form inputs only supposed to be used internally can be used to make OctoPrint move a file that it thinks is a freshly uploaded temporary one into its upload folder.

The following endpoints in OctoPrint are affected:

• /api/files/{local|sdcard}
• /api/languages
• /plugin/backup/restore
• /plugin/pluginmanager/upload_file

Further upload endpoints in third party plugins might be affected too.

The fix removes any internal-only form inputs from incoming requests in the central file upload processor component.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi

Impact

OctoPrint versions up until and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 contain a vulnerability that allows an attacker with the FILE_UPLOAD permission to exfiltrate files from the host that OctoPrint has read access to, by moving them into the upload folder where they then can be downloaded from. This vulnerability was already reported as GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 but the fix provided in OctoPrint 1.11.2 turned out to be incomplete.

The primary risk lies in the potential exfiltration of secrets stored inside OctoPrint's config, or further system files. By removing important runtime files, this could also be used to impact the availability of the host after an attempted server restart. Given that the attacker requires a user account with file upload permissions, the actual impact of this should however hopefully be minimal in most cases.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Details

OctoPrint's web application is implemented in Flask, but uploads are first intercepted by a custom upload handler built on Tornado that sits in front of it. The handler streams the upload to a temporary file on disk - so files larger than the available memory can be uploaded - and rewrites the request, adding internal form fields that tell Flask where to find that temporary file.

These fields are reserved and meant to be set only by the upload handler, never by the client. The previous fix from GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 stripped them from the request received from the client when they were sent as multipart form fields, yet they could still reach Flask through other channels: as plain query parameters, or - since the Tornado handler and Flask did not parse requests identically - smuggled in via several "parser differentials" that looked harmless to the handler while Flask still saw the injected fields. Any of these let an attacker make OctoPrint treat an arbitrary file on the host as a freshly uploaded one and move it into the upload folder.

The following endpoints in OctoPrint are affected:

• /api/files/{local|sdcard}
• /api/languages
• /plugin/backup/restore
• /plugin/pluginmanager/upload_file

Further upload endpoints in third party plugins might be affected too.

The fix rejects requests carrying any of the reserved fields, aligns the Tornado handler's request parsing with Flask's (Werkzeug) to avoid any differential parsing, and re-validates the request rewritten by Tornado before forwarding it to Flask.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Koh Jun Sheng and Jacopo Tediosi.

Timeline

2026-06-04: Report received 2026-06-04: Report acknowledged 2026-06-08: Report verified 2026-06-17: Fix ready for 1.11.x 2026-06-22: Fix ported to 2.0.0 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 are affected by a vulnerability that allows injection of arbitrary HTML and JavaScript into Suppressed Command notifications popups generated by the printer.

An attacker who successfully convinces a victim to print a specially crafted file could exploit this issue to disrupt ongoing prints, extract information (including sensitive configuration settings, if the targeted user has the necessary permissions for that), or perform other actions on behalf of the targeted user within the OctoPrint instance.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Workaround

OctoPrint administrators can mitigate the risk by disabling popups:

• for Action Command notifications, set OctoPrint Settings -> Serial Connection -> Behaviour -> Sanity Checking -> Display notifications for suppressed commands to Never show notifications

It is also strongly recommended to ensure that files being printed originate from trusted sources, and, whenever possible, are sliced with an application's own slicer.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Timeline

2026-03-18: Report received 2026-04-01: Report verified 2026-04-01: Fix ready for 2.0.0 2026-06-22: Fix backported to 1.11.x 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.5 are affected by a (theoretical) timing attack vulnerability that allows API key extraction over the network.

Due to using character based comparison that short-circuits on the first mismatched character during API key validation, rather than a cryptographical method with static runtime regardless of the point of mismatch, an attacker with network based access to an affected OctoPrint could extract API keys valid on the instance by measuring the response times of the denied access responses and guess an API key character by character.

Patches

The vulnerability will be patched in version 1.11.6.

Workaround

The likelihood of this attack actually working is highly dependent on the network's latency, noise and similar parameters. An actual proof of concept was not achieved so far. Still, as always administrators are advised to not expose their OctoPrint instance on hostile networks, especially not on the public Internet!

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Knox Liu.

Impact

OctoPrint versions up to and including 1.11.3 are affected by a vulnerability that allows injection of arbitrary HTML and JavaScript into Action Command notification and prompt popups generated by the printer.

An attacker who successfully convinces a victim to print a specially crafted file could exploit this issue to disrupt ongoing prints, extract information (including sensitive configuration settings, if the targeted user has the necessary permissions for that), or perform other actions on behalf of the targeted user within the OctoPrint instance.

Patches

The vulnerability will be patched in version 1.11.4.

Workaround

OctoPrint administrators can mitigate the risk by disabling popups:

• for Action Command notifications, uncheck OctoPrint Settings -> Printer Notifications -> Enable popups
• for Action Command prompts, set OctoPrint Settings -> Printer Dialogs -> Enable support -> Never

It is also strongly recommended to ensure that files being printed originate from trusted sources, and, whenever possible, are sliced with your own slicer.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Impact

OctoPrint versions up until and including 1.11.2 contain a vulnerability that allows an authenticated attacker to upload a file under a specially crafted filename that will allow arbitrary command execution if said filename becomes included in a command defined in a system event handler and said event gets triggered.

If no event handlers executing system commands with uploaded filenames as parameters have been configured, this vulnerability does not have an impact.

Patches

The vulnerability will be patched in version 1.11.3.

Workaround

Until the patch has been applied, OctoPrint administrators who have event handlers configured that include any kind of filename based placeholders (i.e. {__filename}, {__filepath}, {filename}, {path}, etc -- refer to the events documentation for a full list) should disable those by setting their enabled property to False or unchecking the "Enabled" checkbox in the GUI based Event Manager.

Alternatively, OctoPrint administrators should set feature.enforceReallyUniversalFilenames to true in config.yaml and restart OctoPrint, then vet the existing uploads and make sure to delete any suspicious looking files (e.g. those that contain a ; in their name followed by a command).

As always, OctoPrint administrators are advised to not expose OctoPrint on hostile networks like the public internet, and to vet who has access to their instance.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by @prabhatverma47.

Impact

OctoPrint versions up until and including 1.11.1 contain a vulnerability that allows any unauthenticated attacker to send a manipulated broken multipart/form-data request to OctoPrint and through that make the web server component become unresponsive. This could be used to effectively run a denial of service attack on the OctoPrint server.

Patches

The vulnerability has been patched in version 1.11.2.

Workaround

OctoPrint administrators are once more reminded to not make OctoPrint available on hostile networks (e.g. the internet), regardless of whether this vulnerability is patched or not.

Details

The issue can be triggered by a broken multipart/form-data request lacking an end boundary to any of OctoPrint's endpoints implemented through the octoprint.server.util.tornado.UploadStorageFallbackHandler request handler. The request handler will get stuck in an endless busy loop, looking for a part of the request that will never come. As Tornado is single-threaded, that will effectively block the whole web server.

The fix adds detection of invalid requests like that and ensures they are handled gracefully with an HTTP 400 Bad Request response.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Impact

OctoPrint versions up until and including 1.11.1 contain a vulnerability that allows an attacker with the FILE_UPLOAD permission to exfiltrate files from the host that OctoPrint has read access to, by moving them into the upload folder where they then can be downloaded from.

The primary risk lies in the potential exfiltration of secrets stored inside OctoPrint's config, or further system files. By removing important runtime files, this could also be used to impact the availability of the host. Given that the attacker requires a user account with file upload permissions, the actual impact of this should however hopefully be minimal in most cases.

Patches

The vulnerability has been patched in version 1.11.2.

Details

A specially crafted HTTP Request to an affected upload endpoint that contains some form inputs only supposed to be used internally can be used to make OctoPrint move a file that it thinks is a freshly uploaded temporary one into its upload folder.

The following endpoints in OctoPrint are affected:

• /api/files/{local|sdcard}
• /api/languages
• /plugin/backup/restore
• /plugin/pluginmanager/upload_file

Further upload endpoints in third party plugins might be affected too.

The fix removes any internal-only form inputs from incoming requests in the central file upload processor component.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi

OctoPrint provides a web interface for controlling consumer 3D printers. In versions up to and including 1.10.3, OctoPrint has a vulnerability that allows an attacker to bypass the login redirect and directly access the rendered HTML of certain frontend pages. The primary risk lies in potential future modifications to the codebase that might incorrectly rely on the vulnerable internal functions for authentication checks, leading to security vulnerabilities. This issue has been patched in version 1.11.0.

Impact

OctoPrint versions up until and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 contain a vulnerability that allows an attacker with the FILE_UPLOAD permission to exfiltrate files from the host that OctoPrint has read access to, by moving them into the upload folder where they then can be downloaded from. This vulnerability was already reported as GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 but the fix provided in OctoPrint 1.11.2 turned out to be incomplete.

The primary risk lies in the potential exfiltration of secrets stored inside OctoPrint's config, or further system files. By removing important runtime files, this could also be used to impact the availability of the host after an attempted server restart. Given that the attacker requires a user account with file upload permissions, the actual impact of this should however hopefully be minimal in most cases.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Details

OctoPrint's web application is implemented in Flask, but uploads are first intercepted by a custom upload handler built on Tornado that sits in front of it. The handler streams the upload to a temporary file on disk - so files larger than the available memory can be uploaded - and rewrites the request, adding internal form fields that tell Flask where to find that temporary file.

These fields are reserved and meant to be set only by the upload handler, never by the client. The previous fix from GHSA-m9jh-jf9h-x3h2/CVE-2025-48067 stripped them from the request received from the client when they were sent as multipart form fields, yet they could still reach Flask through other channels: as plain query parameters, or - since the Tornado handler and Flask did not parse requests identically - smuggled in via several "parser differentials" that looked harmless to the handler while Flask still saw the injected fields. Any of these let an attacker make OctoPrint treat an arbitrary file on the host as a freshly uploaded one and move it into the upload folder.

The following endpoints in OctoPrint are affected:

• /api/files/{local|sdcard}
• /api/languages
• /plugin/backup/restore
• /plugin/pluginmanager/upload_file

Further upload endpoints in third party plugins might be affected too.

The fix rejects requests carrying any of the reserved fields, aligns the Tornado handler's request parsing with Flask's (Werkzeug) to avoid any differential parsing, and re-validates the request rewritten by Tornado before forwarding it to Flask.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Koh Jun Sheng and Jacopo Tediosi.

Timeline

2026-06-04: Report received 2026-06-04: Report acknowledged 2026-06-08: Report verified 2026-06-17: Fix ready for 1.11.x 2026-06-22: Fix ported to 2.0.0 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3

Impact

OctoPrint versions up to and including 1.11.7 as well as 2.0.0rc1 and 2.0.0rc2 are affected by a vulnerability that allows injection of arbitrary HTML and JavaScript into Suppressed Command notifications popups generated by the printer.

An attacker who successfully convinces a victim to print a specially crafted file could exploit this issue to disrupt ongoing prints, extract information (including sensitive configuration settings, if the targeted user has the necessary permissions for that), or perform other actions on behalf of the targeted user within the OctoPrint instance.

Patches

The vulnerability has been patched in version 1.11.8 and 2.0.0rc3.

Workaround

OctoPrint administrators can mitigate the risk by disabling popups:

• for Action Command notifications, set OctoPrint Settings -> Serial Connection -> Behaviour -> Sanity Checking -> Display notifications for suppressed commands to Never show notifications

It is also strongly recommended to ensure that files being printed originate from trusted sources, and, whenever possible, are sliced with an application's own slicer.

Credits

This vulnerability was discovered and responsibly disclosed to OctoPrint by Jacopo Tediosi.

Timeline

2026-03-18: Report received 2026-04-01: Report verified 2026-04-01: Fix ready for 2.0.0 2026-06-22: Fix backported to 1.11.x 2026-06-23: Fix released with 1.11.8 and 2.0.0rc3