guzzlehttp/psr7

Impact

guzzlehttp/psr7 did not reject URI host components containing authority delimiters (/, ?, #, @, or \), an embedded port such as host:8080, or IPv6 brackets that do not frame the host (such as [::1 or ::1]). Uri::assertValidHost() rejected only control characters, so these malformed hosts were accepted both when parsing a URI string — including through new Uri(), an absolute-form request target passed to Message::parseRequest(), and the synthetic SERVER_NAME or SERVER_ADDR fallback used by ServerRequest::fromGlobals() — and when setting a host with Uri::withHost(). Because the stored host was not validated, Uri::getHost() could return a value that does not agree with the URI's authority or with the host that is actually used on the wire. For example, Uri::withHost('good.com@evil.com') is accepted, and new Uri('http://[gggg::1]/') produces a getHost() of '[gggg:' while getAuthority() returns '[gggg::1'.

You are affected if your application builds a Uri or calls Uri::withHost() with host data that is wholly or partly attacker-controlled and then relies on Uri::getHost() for a security or routing decision, such as host allowlisting or denylisting, an SSRF guard, cookie scoping, or proxy-bypass selection. You are also affected if you parse, forward, proxy, or re-serialize URIs that come from untrusted raw HTTP messages or from synthetic $_SERVER values. Because getHost() can then disagree with the real connection target, the concrete impact depends on how your application and any downstream HTTP/1.x component use the URI, and may include host-based access-control bypass, server-side request forgery, routing to an unintended host, or Host header confusion. You are not affected if every host you place into a Uri is already trusted and well formed.

Applications using guzzlehttp/guzzle are affected in the same way through Guzzle's use of PSR-7. Guzzle derives the request Host header from the request URI, and its cookie matching and no_proxy proxy-bypass matching both read Uri::getHost(). An application that builds a Guzzle request URI from attacker-controlled host input can therefore have its Host header, cookie scope, or proxy-bypass decision computed against a host that differs from the one Guzzle connects to. This is not the normal request-sending path, and an application that passes only trusted, well-formed URIs to Guzzle and never builds a request URI from attacker-controlled host input is not affected through Guzzle's standard client APIs.

Patches

The issue is patched in 2.12.3 and later. Starting in that release, guzzlehttp/psr7 rejects URI host components that contain authority delimiters, an embedded port, or IPv6 brackets that do not frame the host, both when parsing a URI and via Uri::withHost(), so Uri::getHost() agrees with the URI authority. A framed bracketed literal whose contents are not a valid IPv6 address is preserved rather than rejected, so getHost() still agrees with the authority.

Workarounds

If you cannot upgrade immediately, validate and normalize host values before you build or modify a Uri from untrusted input, and do not treat Uri::getHost() as a trust boundary for a host you have not independently checked. Before passing a host to Uri, reject any value that contains /, ?, #, @, or \, that contains a colon outside a bracketed IPv6 literal, or that has unbalanced brackets. Applications that parse, forward, replay, or re-serialize raw HTTP messages, or that run with attacker-controlled $_SERVER values, should validate the host before calling Message::parseRequest() or ServerRequest::fromGlobals(), and should avoid reparsing untrusted input.

References

• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.3
• https://datatracker.ietf.org/doc/html/rfc6265#section-5.1.3

Impact

guzzlehttp/psr7 did not reject URI host components containing authority delimiters (/, ?, #, @, or \), an embedded port such as host:8080, or IPv6 brackets that do not frame the host (such as [::1 or ::1]). Uri::assertValidHost() rejected only control characters, so these malformed hosts were accepted both when parsing a URI string — including through new Uri(), an absolute-form request target passed to Message::parseRequest(), and the synthetic SERVER_NAME or SERVER_ADDR fallback used by ServerRequest::fromGlobals() — and when setting a host with Uri::withHost(). Because the stored host was not validated, Uri::getHost() could return a value that does not agree with the URI's authority or with the host that is actually used on the wire. For example, Uri::withHost('good.com@evil.com') is accepted, and new Uri('http://[gggg::1]/') produces a getHost() of '[gggg:' while getAuthority() returns '[gggg::1'.

You are affected if your application builds a Uri or calls Uri::withHost() with host data that is wholly or partly attacker-controlled and then relies on Uri::getHost() for a security or routing decision, such as host allowlisting or denylisting, an SSRF guard, cookie scoping, or proxy-bypass selection. You are also affected if you parse, forward, proxy, or re-serialize URIs that come from untrusted raw HTTP messages or from synthetic $_SERVER values. Because getHost() can then disagree with the real connection target, the concrete impact depends on how your application and any downstream HTTP/1.x component use the URI, and may include host-based access-control bypass, server-side request forgery, routing to an unintended host, or Host header confusion. You are not affected if every host you place into a Uri is already trusted and well formed.

Applications using guzzlehttp/guzzle are affected in the same way through Guzzle's use of PSR-7. Guzzle derives the request Host header from the request URI, and its cookie matching and no_proxy proxy-bypass matching both read Uri::getHost(). An application that builds a Guzzle request URI from attacker-controlled host input can therefore have its Host header, cookie scope, or proxy-bypass decision computed against a host that differs from the one Guzzle connects to. This is not the normal request-sending path, and an application that passes only trusted, well-formed URIs to Guzzle and never builds a request URI from attacker-controlled host input is not affected through Guzzle's standard client APIs.

Patches

The issue is patched in 2.12.3 and later. Starting in that release, guzzlehttp/psr7 rejects URI host components that contain authority delimiters, an embedded port, or IPv6 brackets that do not frame the host, both when parsing a URI and via Uri::withHost(), so Uri::getHost() agrees with the URI authority. A framed bracketed literal whose contents are not a valid IPv6 address is preserved rather than rejected, so getHost() still agrees with the authority.

Workarounds

If you cannot upgrade immediately, validate and normalize host values before you build or modify a Uri from untrusted input, and do not treat Uri::getHost() as a trust boundary for a host you have not independently checked. Before passing a host to Uri, reject any value that contains /, ?, #, @, or \, that contains a colon outside a bracketed IPv6 literal, or that has unbalanced brackets. Applications that parse, forward, replay, or re-serialize raw HTTP messages, or that run with attacker-controlled $_SERVER values, should validate the host before calling Message::parseRequest() or ServerRequest::fromGlobals(), and should avoid reparsing untrusted input.

References

• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.3
• https://datatracker.ietf.org/doc/html/rfc6265#section-5.1.3

Impact

guzzlehttp/psr7 did not reject URI host components containing authority delimiters (/, ?, #, @, or \), an embedded port such as host:8080, or IPv6 brackets that do not frame the host (such as [::1 or ::1]). Uri::assertValidHost() rejected only control characters, so these malformed hosts were accepted both when parsing a URI string — including through new Uri(), an absolute-form request target passed to Message::parseRequest(), and the synthetic SERVER_NAME or SERVER_ADDR fallback used by ServerRequest::fromGlobals() — and when setting a host with Uri::withHost(). Because the stored host was not validated, Uri::getHost() could return a value that does not agree with the URI's authority or with the host that is actually used on the wire. For example, Uri::withHost('good.com@evil.com') is accepted, and new Uri('http://[gggg::1]/') produces a getHost() of '[gggg:' while getAuthority() returns '[gggg::1'.

You are affected if your application builds a Uri or calls Uri::withHost() with host data that is wholly or partly attacker-controlled and then relies on Uri::getHost() for a security or routing decision, such as host allowlisting or denylisting, an SSRF guard, cookie scoping, or proxy-bypass selection. You are also affected if you parse, forward, proxy, or re-serialize URIs that come from untrusted raw HTTP messages or from synthetic $_SERVER values. Because getHost() can then disagree with the real connection target, the concrete impact depends on how your application and any downstream HTTP/1.x component use the URI, and may include host-based access-control bypass, server-side request forgery, routing to an unintended host, or Host header confusion. You are not affected if every host you place into a Uri is already trusted and well formed.

Applications using guzzlehttp/guzzle are affected in the same way through Guzzle's use of PSR-7. Guzzle derives the request Host header from the request URI, and its cookie matching and no_proxy proxy-bypass matching both read Uri::getHost(). An application that builds a Guzzle request URI from attacker-controlled host input can therefore have its Host header, cookie scope, or proxy-bypass decision computed against a host that differs from the one Guzzle connects to. This is not the normal request-sending path, and an application that passes only trusted, well-formed URIs to Guzzle and never builds a request URI from attacker-controlled host input is not affected through Guzzle's standard client APIs.

Patches

The issue is patched in 2.12.3 and later. Starting in that release, guzzlehttp/psr7 rejects URI host components that contain authority delimiters, an embedded port, or IPv6 brackets that do not frame the host, both when parsing a URI and via Uri::withHost(), so Uri::getHost() agrees with the URI authority. A framed bracketed literal whose contents are not a valid IPv6 address is preserved rather than rejected, so getHost() still agrees with the authority.

Workarounds

If you cannot upgrade immediately, validate and normalize host values before you build or modify a Uri from untrusted input, and do not treat Uri::getHost() as a trust boundary for a host you have not independently checked. Before passing a host to Uri, reject any value that contains /, ?, #, @, or \, that contains a colon outside a bracketed IPv6 literal, or that has unbalanced brackets. Applications that parse, forward, replay, or re-serialize raw HTTP messages, or that run with attacker-controlled $_SERVER values, should validate the host before calling Message::parseRequest() or ServerRequest::fromGlobals(), and should avoid reparsing untrusted input.

References

• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.3
• https://datatracker.ietf.org/doc/html/rfc6265#section-5.1.3

Impact

guzzlehttp/psr7 did not reject CR/LF characters in certain first-party HTTP start-line fields: the request method, protocol version, and response reason phrase. If an application placed attacker-controlled data into one of those fields and later serialized the PSR-7 message as raw HTTP/1.x, for example with Message::toString() or an equivalent serializer, the serialized message could contain attacker-controlled header lines. The issue can also be reached through Message::parseRequest() or Message::parseResponse() when malformed raw messages are parsed into first-party PSR-7 objects and then serialized again.

Creating or modifying a Request, Response, or other PSR-7 object alone is not sufficient. The issue requires the malformed message to be serialized and written to the network, forwarded, replayed, or otherwise processed by software that does not independently reject the malformed start line. This is not the normal request-sending path used by guzzlehttp/guzzle; applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected.

Applications are most likely to be affected when they manually serialize PSR-7 messages, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, testing, or similar code. Depending on how downstream HTTP/1.1 components parse the serialized message, this may lead to header injection, response splitting, request smuggling, or cache poisoning.

Patches

The issue is patched in 2.12.1 and later. Starting in that release, guzzlehttp/psr7 rejects CR/LF characters in HTTP method, protocol version, and response reason phrase values before storing them in first-party message objects.

Workarounds

If you cannot upgrade immediately, reject CR/LF in untrusted method, protocol version, and reason phrase values before constructing or modifying PSR-7 messages.

Applications that parse, forward, replay, or serialize raw HTTP messages cannot work around the parser entry points by validating only after parsing. They should validate the raw start line before calling Message::parseRequest() or Message::parseResponse(), avoid reparsing untrusted raw messages, or upgrade. If an application runs with attacker-controlled synthetic $_SERVER values, validate REQUEST_METHOD and SERVER_PROTOCOL before calling ServerRequest::fromGlobals().

Impact

guzzlehttp/psr7 did not reject URI host components containing authority delimiters (/, ?, #, @, or \), an embedded port such as host:8080, or IPv6 brackets that do not frame the host (such as [::1 or ::1]). Uri::assertValidHost() rejected only control characters, so these malformed hosts were accepted both when parsing a URI string — including through new Uri(), an absolute-form request target passed to Message::parseRequest(), and the synthetic SERVER_NAME or SERVER_ADDR fallback used by ServerRequest::fromGlobals() — and when setting a host with Uri::withHost(). Because the stored host was not validated, Uri::getHost() could return a value that does not agree with the URI's authority or with the host that is actually used on the wire. For example, Uri::withHost('good.com@evil.com') is accepted, and new Uri('http://[gggg::1]/') produces a getHost() of '[gggg:' while getAuthority() returns '[gggg::1'.

You are affected if your application builds a Uri or calls Uri::withHost() with host data that is wholly or partly attacker-controlled and then relies on Uri::getHost() for a security or routing decision, such as host allowlisting or denylisting, an SSRF guard, cookie scoping, or proxy-bypass selection. You are also affected if you parse, forward, proxy, or re-serialize URIs that come from untrusted raw HTTP messages or from synthetic $_SERVER values. Because getHost() can then disagree with the real connection target, the concrete impact depends on how your application and any downstream HTTP/1.x component use the URI, and may include host-based access-control bypass, server-side request forgery, routing to an unintended host, or Host header confusion. You are not affected if every host you place into a Uri is already trusted and well formed.

Applications using guzzlehttp/guzzle are affected in the same way through Guzzle's use of PSR-7. Guzzle derives the request Host header from the request URI, and its cookie matching and no_proxy proxy-bypass matching both read Uri::getHost(). An application that builds a Guzzle request URI from attacker-controlled host input can therefore have its Host header, cookie scope, or proxy-bypass decision computed against a host that differs from the one Guzzle connects to. This is not the normal request-sending path, and an application that passes only trusted, well-formed URIs to Guzzle and never builds a request URI from attacker-controlled host input is not affected through Guzzle's standard client APIs.

Patches

The issue is patched in 2.12.3 and later. Starting in that release, guzzlehttp/psr7 rejects URI host components that contain authority delimiters, an embedded port, or IPv6 brackets that do not frame the host, both when parsing a URI and via Uri::withHost(), so Uri::getHost() agrees with the URI authority. A framed bracketed literal whose contents are not a valid IPv6 address is preserved rather than rejected, so getHost() still agrees with the authority.

Workarounds

If you cannot upgrade immediately, validate and normalize host values before you build or modify a Uri from untrusted input, and do not treat Uri::getHost() as a trust boundary for a host you have not independently checked. Before passing a host to Uri, reject any value that contains /, ?, #, @, or \, that contains a colon outside a bracketed IPv6 literal, or that has unbalanced brackets. Applications that parse, forward, replay, or re-serialize raw HTTP messages, or that run with attacker-controlled $_SERVER values, should validate the host before calling Message::parseRequest() or ServerRequest::fromGlobals(), and should avoid reparsing untrusted input.

References

• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.3
• https://datatracker.ietf.org/doc/html/rfc6265#section-5.1.3

Impact

guzzlehttp/psr7 did not reject CR/LF characters in certain first-party HTTP start-line fields: the request method, protocol version, and response reason phrase. If an application placed attacker-controlled data into one of those fields and later serialized the PSR-7 message as raw HTTP/1.x, for example with Message::toString() or an equivalent serializer, the serialized message could contain attacker-controlled header lines. The issue can also be reached through Message::parseRequest() or Message::parseResponse() when malformed raw messages are parsed into first-party PSR-7 objects and then serialized again.

Creating or modifying a Request, Response, or other PSR-7 object alone is not sufficient. The issue requires the malformed message to be serialized and written to the network, forwarded, replayed, or otherwise processed by software that does not independently reject the malformed start line. This is not the normal request-sending path used by guzzlehttp/guzzle; applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected.

Applications are most likely to be affected when they manually serialize PSR-7 messages, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, testing, or similar code. Depending on how downstream HTTP/1.1 components parse the serialized message, this may lead to header injection, response splitting, request smuggling, or cache poisoning.

Patches

The issue is patched in 2.12.1 and later. Starting in that release, guzzlehttp/psr7 rejects CR/LF characters in HTTP method, protocol version, and response reason phrase values before storing them in first-party message objects.

Workarounds

If you cannot upgrade immediately, reject CR/LF in untrusted method, protocol version, and reason phrase values before constructing or modifying PSR-7 messages.

Applications that parse, forward, replay, or serialize raw HTTP messages cannot work around the parser entry points by validating only after parsing. They should validate the raw start line before calling Message::parseRequest() or Message::parseResponse(), avoid reparsing untrusted raw messages, or upgrade. If an application runs with attacker-controlled synthetic $_SERVER values, validate REQUEST_METHOD and SERVER_PROTOCOL before calling ServerRequest::fromGlobals().

Impact

guzzlehttp/psr7 did not reject URI host components containing authority delimiters (/, ?, #, @, or \), an embedded port such as host:8080, or IPv6 brackets that do not frame the host (such as [::1 or ::1]). Uri::assertValidHost() rejected only control characters, so these malformed hosts were accepted both when parsing a URI string — including through new Uri(), an absolute-form request target passed to Message::parseRequest(), and the synthetic SERVER_NAME or SERVER_ADDR fallback used by ServerRequest::fromGlobals() — and when setting a host with Uri::withHost(). Because the stored host was not validated, Uri::getHost() could return a value that does not agree with the URI's authority or with the host that is actually used on the wire. For example, Uri::withHost('good.com@evil.com') is accepted, and new Uri('http://[gggg::1]/') produces a getHost() of '[gggg:' while getAuthority() returns '[gggg::1'.

You are affected if your application builds a Uri or calls Uri::withHost() with host data that is wholly or partly attacker-controlled and then relies on Uri::getHost() for a security or routing decision, such as host allowlisting or denylisting, an SSRF guard, cookie scoping, or proxy-bypass selection. You are also affected if you parse, forward, proxy, or re-serialize URIs that come from untrusted raw HTTP messages or from synthetic $_SERVER values. Because getHost() can then disagree with the real connection target, the concrete impact depends on how your application and any downstream HTTP/1.x component use the URI, and may include host-based access-control bypass, server-side request forgery, routing to an unintended host, or Host header confusion. You are not affected if every host you place into a Uri is already trusted and well formed.

Applications using guzzlehttp/guzzle are affected in the same way through Guzzle's use of PSR-7. Guzzle derives the request Host header from the request URI, and its cookie matching and no_proxy proxy-bypass matching both read Uri::getHost(). An application that builds a Guzzle request URI from attacker-controlled host input can therefore have its Host header, cookie scope, or proxy-bypass decision computed against a host that differs from the one Guzzle connects to. This is not the normal request-sending path, and an application that passes only trusted, well-formed URIs to Guzzle and never builds a request URI from attacker-controlled host input is not affected through Guzzle's standard client APIs.

Patches

The issue is patched in 2.12.3 and later. Starting in that release, guzzlehttp/psr7 rejects URI host components that contain authority delimiters, an embedded port, or IPv6 brackets that do not frame the host, both when parsing a URI and via Uri::withHost(), so Uri::getHost() agrees with the URI authority. A framed bracketed literal whose contents are not a valid IPv6 address is preserved rather than rejected, so getHost() still agrees with the authority.

Workarounds

If you cannot upgrade immediately, validate and normalize host values before you build or modify a Uri from untrusted input, and do not treat Uri::getHost() as a trust boundary for a host you have not independently checked. Before passing a host to Uri, reject any value that contains /, ?, #, @, or \, that contains a colon outside a bracketed IPv6 literal, or that has unbalanced brackets. Applications that parse, forward, replay, or re-serialize raw HTTP messages, or that run with attacker-controlled $_SERVER values, should validate the host before calling Message::parseRequest() or ServerRequest::fromGlobals(), and should avoid reparsing untrusted input.

References

• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.3
• https://datatracker.ietf.org/doc/html/rfc6265#section-5.1.3

Impact

guzzlehttp/psr7 did not reject CR/LF characters in certain first-party HTTP start-line fields: the request method, protocol version, and response reason phrase. If an application placed attacker-controlled data into one of those fields and later serialized the PSR-7 message as raw HTTP/1.x, for example with Message::toString() or an equivalent serializer, the serialized message could contain attacker-controlled header lines. The issue can also be reached through Message::parseRequest() or Message::parseResponse() when malformed raw messages are parsed into first-party PSR-7 objects and then serialized again.

Creating or modifying a Request, Response, or other PSR-7 object alone is not sufficient. The issue requires the malformed message to be serialized and written to the network, forwarded, replayed, or otherwise processed by software that does not independently reject the malformed start line. This is not the normal request-sending path used by guzzlehttp/guzzle; applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected.

Applications are most likely to be affected when they manually serialize PSR-7 messages, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, testing, or similar code. Depending on how downstream HTTP/1.1 components parse the serialized message, this may lead to header injection, response splitting, request smuggling, or cache poisoning.

Patches

The issue is patched in 2.12.1 and later. Starting in that release, guzzlehttp/psr7 rejects CR/LF characters in HTTP method, protocol version, and response reason phrase values before storing them in first-party message objects.

Workarounds

If you cannot upgrade immediately, reject CR/LF in untrusted method, protocol version, and reason phrase values before constructing or modifying PSR-7 messages.

Applications that parse, forward, replay, or serialize raw HTTP messages cannot work around the parser entry points by validating only after parsing. They should validate the raw start line before calling Message::parseRequest() or Message::parseResponse(), avoid reparsing untrusted raw messages, or upgrade. If an application runs with attacker-controlled synthetic $_SERVER values, validate REQUEST_METHOD and SERVER_PROTOCOL before calling ServerRequest::fromGlobals().

Impact

guzzlehttp/psr7 did not reject URI host components containing authority delimiters (/, ?, #, @, or \), an embedded port such as host:8080, or IPv6 brackets that do not frame the host (such as [::1 or ::1]). Uri::assertValidHost() rejected only control characters, so these malformed hosts were accepted both when parsing a URI string — including through new Uri(), an absolute-form request target passed to Message::parseRequest(), and the synthetic SERVER_NAME or SERVER_ADDR fallback used by ServerRequest::fromGlobals() — and when setting a host with Uri::withHost(). Because the stored host was not validated, Uri::getHost() could return a value that does not agree with the URI's authority or with the host that is actually used on the wire. For example, Uri::withHost('good.com@evil.com') is accepted, and new Uri('http://[gggg::1]/') produces a getHost() of '[gggg:' while getAuthority() returns '[gggg::1'.

You are affected if your application builds a Uri or calls Uri::withHost() with host data that is wholly or partly attacker-controlled and then relies on Uri::getHost() for a security or routing decision, such as host allowlisting or denylisting, an SSRF guard, cookie scoping, or proxy-bypass selection. You are also affected if you parse, forward, proxy, or re-serialize URIs that come from untrusted raw HTTP messages or from synthetic $_SERVER values. Because getHost() can then disagree with the real connection target, the concrete impact depends on how your application and any downstream HTTP/1.x component use the URI, and may include host-based access-control bypass, server-side request forgery, routing to an unintended host, or Host header confusion. You are not affected if every host you place into a Uri is already trusted and well formed.

Applications using guzzlehttp/guzzle are affected in the same way through Guzzle's use of PSR-7. Guzzle derives the request Host header from the request URI, and its cookie matching and no_proxy proxy-bypass matching both read Uri::getHost(). An application that builds a Guzzle request URI from attacker-controlled host input can therefore have its Host header, cookie scope, or proxy-bypass decision computed against a host that differs from the one Guzzle connects to. This is not the normal request-sending path, and an application that passes only trusted, well-formed URIs to Guzzle and never builds a request URI from attacker-controlled host input is not affected through Guzzle's standard client APIs.

Patches

The issue is patched in 2.12.3 and later. Starting in that release, guzzlehttp/psr7 rejects URI host components that contain authority delimiters, an embedded port, or IPv6 brackets that do not frame the host, both when parsing a URI and via Uri::withHost(), so Uri::getHost() agrees with the URI authority. A framed bracketed literal whose contents are not a valid IPv6 address is preserved rather than rejected, so getHost() still agrees with the authority.

Workarounds

If you cannot upgrade immediately, validate and normalize host values before you build or modify a Uri from untrusted input, and do not treat Uri::getHost() as a trust boundary for a host you have not independently checked. Before passing a host to Uri, reject any value that contains /, ?, #, @, or \, that contains a colon outside a bracketed IPv6 literal, or that has unbalanced brackets. Applications that parse, forward, replay, or re-serialize raw HTTP messages, or that run with attacker-controlled $_SERVER values, should validate the host before calling Message::parseRequest() or ServerRequest::fromGlobals(), and should avoid reparsing untrusted input.

References

• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.3
• https://datatracker.ietf.org/doc/html/rfc6265#section-5.1.3

Impact

guzzlehttp/psr7 did not reject CR/LF characters in certain first-party HTTP start-line fields: the request method, protocol version, and response reason phrase. If an application placed attacker-controlled data into one of those fields and later serialized the PSR-7 message as raw HTTP/1.x, for example with Message::toString() or an equivalent serializer, the serialized message could contain attacker-controlled header lines. The issue can also be reached through Message::parseRequest() or Message::parseResponse() when malformed raw messages are parsed into first-party PSR-7 objects and then serialized again.

Creating or modifying a Request, Response, or other PSR-7 object alone is not sufficient. The issue requires the malformed message to be serialized and written to the network, forwarded, replayed, or otherwise processed by software that does not independently reject the malformed start line. This is not the normal request-sending path used by guzzlehttp/guzzle; applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected.

Applications are most likely to be affected when they manually serialize PSR-7 messages, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, testing, or similar code. Depending on how downstream HTTP/1.1 components parse the serialized message, this may lead to header injection, response splitting, request smuggling, or cache poisoning.

Patches

The issue is patched in 2.12.1 and later. Starting in that release, guzzlehttp/psr7 rejects CR/LF characters in HTTP method, protocol version, and response reason phrase values before storing them in first-party message objects.

Workarounds

If you cannot upgrade immediately, reject CR/LF in untrusted method, protocol version, and reason phrase values before constructing or modifying PSR-7 messages.

Applications that parse, forward, replay, or serialize raw HTTP messages cannot work around the parser entry points by validating only after parsing. They should validate the raw start line before calling Message::parseRequest() or Message::parseResponse(), avoid reparsing untrusted raw messages, or upgrade. If an application runs with attacker-controlled synthetic $_SERVER values, validate REQUEST_METHOD and SERVER_PROTOCOL before calling ServerRequest::fromGlobals().

Impact

guzzlehttp/psr7 did not reject URI host components containing authority delimiters (/, ?, #, @, or \), an embedded port such as host:8080, or IPv6 brackets that do not frame the host (such as [::1 or ::1]). Uri::assertValidHost() rejected only control characters, so these malformed hosts were accepted both when parsing a URI string — including through new Uri(), an absolute-form request target passed to Message::parseRequest(), and the synthetic SERVER_NAME or SERVER_ADDR fallback used by ServerRequest::fromGlobals() — and when setting a host with Uri::withHost(). Because the stored host was not validated, Uri::getHost() could return a value that does not agree with the URI's authority or with the host that is actually used on the wire. For example, Uri::withHost('good.com@evil.com') is accepted, and new Uri('http://[gggg::1]/') produces a getHost() of '[gggg:' while getAuthority() returns '[gggg::1'.

You are affected if your application builds a Uri or calls Uri::withHost() with host data that is wholly or partly attacker-controlled and then relies on Uri::getHost() for a security or routing decision, such as host allowlisting or denylisting, an SSRF guard, cookie scoping, or proxy-bypass selection. You are also affected if you parse, forward, proxy, or re-serialize URIs that come from untrusted raw HTTP messages or from synthetic $_SERVER values. Because getHost() can then disagree with the real connection target, the concrete impact depends on how your application and any downstream HTTP/1.x component use the URI, and may include host-based access-control bypass, server-side request forgery, routing to an unintended host, or Host header confusion. You are not affected if every host you place into a Uri is already trusted and well formed.

Applications using guzzlehttp/guzzle are affected in the same way through Guzzle's use of PSR-7. Guzzle derives the request Host header from the request URI, and its cookie matching and no_proxy proxy-bypass matching both read Uri::getHost(). An application that builds a Guzzle request URI from attacker-controlled host input can therefore have its Host header, cookie scope, or proxy-bypass decision computed against a host that differs from the one Guzzle connects to. This is not the normal request-sending path, and an application that passes only trusted, well-formed URIs to Guzzle and never builds a request URI from attacker-controlled host input is not affected through Guzzle's standard client APIs.

Patches

The issue is patched in 2.12.3 and later. Starting in that release, guzzlehttp/psr7 rejects URI host components that contain authority delimiters, an embedded port, or IPv6 brackets that do not frame the host, both when parsing a URI and via Uri::withHost(), so Uri::getHost() agrees with the URI authority. A framed bracketed literal whose contents are not a valid IPv6 address is preserved rather than rejected, so getHost() still agrees with the authority.

Workarounds

If you cannot upgrade immediately, validate and normalize host values before you build or modify a Uri from untrusted input, and do not treat Uri::getHost() as a trust boundary for a host you have not independently checked. Before passing a host to Uri, reject any value that contains /, ?, #, @, or \, that contains a colon outside a bracketed IPv6 literal, or that has unbalanced brackets. Applications that parse, forward, replay, or re-serialize raw HTTP messages, or that run with attacker-controlled $_SERVER values, should validate the host before calling Message::parseRequest() or ServerRequest::fromGlobals(), and should avoid reparsing untrusted input.

References

• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.3
• https://datatracker.ietf.org/doc/html/rfc6265#section-5.1.3

Impact

guzzlehttp/psr7 did not reject CR/LF characters in certain first-party HTTP start-line fields: the request method, protocol version, and response reason phrase. If an application placed attacker-controlled data into one of those fields and later serialized the PSR-7 message as raw HTTP/1.x, for example with Message::toString() or an equivalent serializer, the serialized message could contain attacker-controlled header lines. The issue can also be reached through Message::parseRequest() or Message::parseResponse() when malformed raw messages are parsed into first-party PSR-7 objects and then serialized again.

Creating or modifying a Request, Response, or other PSR-7 object alone is not sufficient. The issue requires the malformed message to be serialized and written to the network, forwarded, replayed, or otherwise processed by software that does not independently reject the malformed start line. This is not the normal request-sending path used by guzzlehttp/guzzle; applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected.

Applications are most likely to be affected when they manually serialize PSR-7 messages, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, testing, or similar code. Depending on how downstream HTTP/1.1 components parse the serialized message, this may lead to header injection, response splitting, request smuggling, or cache poisoning.

Patches

The issue is patched in 2.12.1 and later. Starting in that release, guzzlehttp/psr7 rejects CR/LF characters in HTTP method, protocol version, and response reason phrase values before storing them in first-party message objects.

Workarounds

If you cannot upgrade immediately, reject CR/LF in untrusted method, protocol version, and reason phrase values before constructing or modifying PSR-7 messages.

Applications that parse, forward, replay, or serialize raw HTTP messages cannot work around the parser entry points by validating only after parsing. They should validate the raw start line before calling Message::parseRequest() or Message::parseResponse(), avoid reparsing untrusted raw messages, or upgrade. If an application runs with attacker-controlled synthetic $_SERVER values, validate REQUEST_METHOD and SERVER_PROTOCOL before calling ServerRequest::fromGlobals().

Impact

guzzlehttp/psr7 did not reject URI host components containing authority delimiters (/, ?, #, @, or \), an embedded port such as host:8080, or IPv6 brackets that do not frame the host (such as [::1 or ::1]). Uri::assertValidHost() rejected only control characters, so these malformed hosts were accepted both when parsing a URI string — including through new Uri(), an absolute-form request target passed to Message::parseRequest(), and the synthetic SERVER_NAME or SERVER_ADDR fallback used by ServerRequest::fromGlobals() — and when setting a host with Uri::withHost(). Because the stored host was not validated, Uri::getHost() could return a value that does not agree with the URI's authority or with the host that is actually used on the wire. For example, Uri::withHost('good.com@evil.com') is accepted, and new Uri('http://[gggg::1]/') produces a getHost() of '[gggg:' while getAuthority() returns '[gggg::1'.

You are affected if your application builds a Uri or calls Uri::withHost() with host data that is wholly or partly attacker-controlled and then relies on Uri::getHost() for a security or routing decision, such as host allowlisting or denylisting, an SSRF guard, cookie scoping, or proxy-bypass selection. You are also affected if you parse, forward, proxy, or re-serialize URIs that come from untrusted raw HTTP messages or from synthetic $_SERVER values. Because getHost() can then disagree with the real connection target, the concrete impact depends on how your application and any downstream HTTP/1.x component use the URI, and may include host-based access-control bypass, server-side request forgery, routing to an unintended host, or Host header confusion. You are not affected if every host you place into a Uri is already trusted and well formed.

Applications using guzzlehttp/guzzle are affected in the same way through Guzzle's use of PSR-7. Guzzle derives the request Host header from the request URI, and its cookie matching and no_proxy proxy-bypass matching both read Uri::getHost(). An application that builds a Guzzle request URI from attacker-controlled host input can therefore have its Host header, cookie scope, or proxy-bypass decision computed against a host that differs from the one Guzzle connects to. This is not the normal request-sending path, and an application that passes only trusted, well-formed URIs to Guzzle and never builds a request URI from attacker-controlled host input is not affected through Guzzle's standard client APIs.

Patches

The issue is patched in 2.12.3 and later. Starting in that release, guzzlehttp/psr7 rejects URI host components that contain authority delimiters, an embedded port, or IPv6 brackets that do not frame the host, both when parsing a URI and via Uri::withHost(), so Uri::getHost() agrees with the URI authority. A framed bracketed literal whose contents are not a valid IPv6 address is preserved rather than rejected, so getHost() still agrees with the authority.

Workarounds

If you cannot upgrade immediately, validate and normalize host values before you build or modify a Uri from untrusted input, and do not treat Uri::getHost() as a trust boundary for a host you have not independently checked. Before passing a host to Uri, reject any value that contains /, ?, #, @, or \, that contains a colon outside a bracketed IPv6 literal, or that has unbalanced brackets. Applications that parse, forward, replay, or re-serialize raw HTTP messages, or that run with attacker-controlled $_SERVER values, should validate the host before calling Message::parseRequest() or ServerRequest::fromGlobals(), and should avoid reparsing untrusted input.

References

• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.3
• https://datatracker.ietf.org/doc/html/rfc6265#section-5.1.3

Impact

guzzlehttp/psr7 did not reject CR/LF characters in certain first-party HTTP start-line fields: the request method, protocol version, and response reason phrase. If an application placed attacker-controlled data into one of those fields and later serialized the PSR-7 message as raw HTTP/1.x, for example with Message::toString() or an equivalent serializer, the serialized message could contain attacker-controlled header lines. The issue can also be reached through Message::parseRequest() or Message::parseResponse() when malformed raw messages are parsed into first-party PSR-7 objects and then serialized again.

Creating or modifying a Request, Response, or other PSR-7 object alone is not sufficient. The issue requires the malformed message to be serialized and written to the network, forwarded, replayed, or otherwise processed by software that does not independently reject the malformed start line. This is not the normal request-sending path used by guzzlehttp/guzzle; applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected.

Applications are most likely to be affected when they manually serialize PSR-7 messages, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, testing, or similar code. Depending on how downstream HTTP/1.1 components parse the serialized message, this may lead to header injection, response splitting, request smuggling, or cache poisoning.

Patches

The issue is patched in 2.12.1 and later. Starting in that release, guzzlehttp/psr7 rejects CR/LF characters in HTTP method, protocol version, and response reason phrase values before storing them in first-party message objects.

Workarounds

If you cannot upgrade immediately, reject CR/LF in untrusted method, protocol version, and reason phrase values before constructing or modifying PSR-7 messages.

Applications that parse, forward, replay, or serialize raw HTTP messages cannot work around the parser entry points by validating only after parsing. They should validate the raw start line before calling Message::parseRequest() or Message::parseResponse(), avoid reparsing untrusted raw messages, or upgrade. If an application runs with attacker-controlled synthetic $_SERVER values, validate REQUEST_METHOD and SERVER_PROTOCOL before calling ServerRequest::fromGlobals().

Impact

guzzlehttp/psr7 did not reject URI host components containing authority delimiters (/, ?, #, @, or \), an embedded port such as host:8080, or IPv6 brackets that do not frame the host (such as [::1 or ::1]). Uri::assertValidHost() rejected only control characters, so these malformed hosts were accepted both when parsing a URI string — including through new Uri(), an absolute-form request target passed to Message::parseRequest(), and the synthetic SERVER_NAME or SERVER_ADDR fallback used by ServerRequest::fromGlobals() — and when setting a host with Uri::withHost(). Because the stored host was not validated, Uri::getHost() could return a value that does not agree with the URI's authority or with the host that is actually used on the wire. For example, Uri::withHost('good.com@evil.com') is accepted, and new Uri('http://[gggg::1]/') produces a getHost() of '[gggg:' while getAuthority() returns '[gggg::1'.

You are affected if your application builds a Uri or calls Uri::withHost() with host data that is wholly or partly attacker-controlled and then relies on Uri::getHost() for a security or routing decision, such as host allowlisting or denylisting, an SSRF guard, cookie scoping, or proxy-bypass selection. You are also affected if you parse, forward, proxy, or re-serialize URIs that come from untrusted raw HTTP messages or from synthetic $_SERVER values. Because getHost() can then disagree with the real connection target, the concrete impact depends on how your application and any downstream HTTP/1.x component use the URI, and may include host-based access-control bypass, server-side request forgery, routing to an unintended host, or Host header confusion. You are not affected if every host you place into a Uri is already trusted and well formed.

Applications using guzzlehttp/guzzle are affected in the same way through Guzzle's use of PSR-7. Guzzle derives the request Host header from the request URI, and its cookie matching and no_proxy proxy-bypass matching both read Uri::getHost(). An application that builds a Guzzle request URI from attacker-controlled host input can therefore have its Host header, cookie scope, or proxy-bypass decision computed against a host that differs from the one Guzzle connects to. This is not the normal request-sending path, and an application that passes only trusted, well-formed URIs to Guzzle and never builds a request URI from attacker-controlled host input is not affected through Guzzle's standard client APIs.

Patches

The issue is patched in 2.12.3 and later. Starting in that release, guzzlehttp/psr7 rejects URI host components that contain authority delimiters, an embedded port, or IPv6 brackets that do not frame the host, both when parsing a URI and via Uri::withHost(), so Uri::getHost() agrees with the URI authority. A framed bracketed literal whose contents are not a valid IPv6 address is preserved rather than rejected, so getHost() still agrees with the authority.

Workarounds

If you cannot upgrade immediately, validate and normalize host values before you build or modify a Uri from untrusted input, and do not treat Uri::getHost() as a trust boundary for a host you have not independently checked. Before passing a host to Uri, reject any value that contains /, ?, #, @, or \, that contains a colon outside a bracketed IPv6 literal, or that has unbalanced brackets. Applications that parse, forward, replay, or re-serialize raw HTTP messages, or that run with attacker-controlled $_SERVER values, should validate the host before calling Message::parseRequest() or ServerRequest::fromGlobals(), and should avoid reparsing untrusted input.

References

• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.3
• https://datatracker.ietf.org/doc/html/rfc6265#section-5.1.3

Impact

guzzlehttp/psr7 did not reject CR/LF characters in certain first-party HTTP start-line fields: the request method, protocol version, and response reason phrase. If an application placed attacker-controlled data into one of those fields and later serialized the PSR-7 message as raw HTTP/1.x, for example with Message::toString() or an equivalent serializer, the serialized message could contain attacker-controlled header lines. The issue can also be reached through Message::parseRequest() or Message::parseResponse() when malformed raw messages are parsed into first-party PSR-7 objects and then serialized again.

Creating or modifying a Request, Response, or other PSR-7 object alone is not sufficient. The issue requires the malformed message to be serialized and written to the network, forwarded, replayed, or otherwise processed by software that does not independently reject the malformed start line. This is not the normal request-sending path used by guzzlehttp/guzzle; applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected.

Applications are most likely to be affected when they manually serialize PSR-7 messages, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, testing, or similar code. Depending on how downstream HTTP/1.1 components parse the serialized message, this may lead to header injection, response splitting, request smuggling, or cache poisoning.

Patches

The issue is patched in 2.12.1 and later. Starting in that release, guzzlehttp/psr7 rejects CR/LF characters in HTTP method, protocol version, and response reason phrase values before storing them in first-party message objects.

Workarounds

If you cannot upgrade immediately, reject CR/LF in untrusted method, protocol version, and reason phrase values before constructing or modifying PSR-7 messages.

Applications that parse, forward, replay, or serialize raw HTTP messages cannot work around the parser entry points by validating only after parsing. They should validate the raw start line before calling Message::parseRequest() or Message::parseResponse(), avoid reparsing untrusted raw messages, or upgrade. If an application runs with attacker-controlled synthetic $_SERVER values, validate REQUEST_METHOD and SERVER_PROTOCOL before calling ServerRequest::fromGlobals().

Impact

guzzlehttp/psr7 improperly interpreted malformed Host header values when constructing request URIs from inbound request data. This issue concerns inbound request parsing and server request construction. It does not require serializing a PSR-7 request, and it is not part of the normal outbound request-sending path used by guzzlehttp/guzzle.

A vulnerable flow is:

1. An attacker controls a raw HTTP request or server variable containing a Host value.
2. The Host value contains URI authority delimiters, such as trusted.example@evil.example.
3. guzzlehttp/psr7 uses that value to construct a URI.
4. The URI parser treats the portion before @ as userinfo and the portion after @ as the URI host.
5. The resulting PSR-7 request URI host differs from the original Host header value.

For example, Host: trusted.example@evil.example can result in a PSR-7 URI whose host is evil.example, while the original Host header value remains trusted.example@evil.example.

Applications are affected if they parse attacker-controlled raw HTTP requests with GuzzleHttp\Psr7\Message::parseRequest() or the legacy 1.x GuzzleHttp\Psr7\parse_request() function, or if they build server requests from attacker-controlled server variables with GuzzleHttp\Psr7\ServerRequest::fromGlobals() or GuzzleHttp\Psr7\ServerRequest::getUriFromGlobals(), and then rely on the resulting URI host for routing, allow-list checks, credential selection, or forwarding decisions. Applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected. In affected forwarding or gateway scenarios, this may cause requests or credentials to be sent to an unintended host.

Patches

The issue is patched in 2.10.2 and later. 1.x is end-of-life and will not receive a patch.

Workarounds

If you cannot upgrade immediately, validate Host values before passing untrusted request data to Message::parseRequest(), legacy 1.x parse_request(), ServerRequest::fromGlobals(), or ServerRequest::getUriFromGlobals().

Accept only uri-host [ ":" port ]. Reject values containing whitespace, control characters, userinfo (@), path (/ or \), query (?), fragment (#), malformed IP literals or bracket syntax, or invalid port syntax.

Do not validate Host by prefixing it with http:// and passing it to parse_url(), because that can reinterpret malformed values as URI userinfo and host.

References

• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.2
• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.3
• https://www.rfc-editor.org/rfc/rfc9110.html#section-4.2.4
• https://www.rfc-editor.org/rfc/rfc9110.html#section-7.2

Impact

guzzlehttp/psr7 did not reject ASCII control characters, whitespace, or DEL in first-party URI host components. The issue requires a PSR-7 request to be serialized into a raw HTTP/1.x message, for example with GuzzleHttp\Psr7\Message::toString() or an equivalent custom serializer. Creating a Uri, Request, or other PSR-7 object alone is not sufficient. The malformed host must be copied into the serialized Host header without further validation.

A vulnerable flow is:

1. An application accepts a user-controlled URL.
2. The URL is used to construct a PSR-7 Uri or Request.
3. The host component contains CRLF or another header-unsafe character.
4. The request is serialized into a raw HTTP/1.x message without an explicit Host header.
5. The host is copied into the serialized Host header.
6. The serialized request is written to the network or otherwise processed by software that does not independently reject the malformed host.

In that flow, an attacker can cause the serialized request to contain additional attacker-controlled header lines. For example, a host containing "\r\nX-Injected: yes" can cause the generated Host header to span multiple HTTP header lines.

This is not the normal request-sending path used by guzzlehttp/guzzle. Applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected. Applications are most likely to be affected when they manually serialize PSR-7 requests, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, or similar request-dispatch code that serializes requests without independently validating URI hosts and header data. In deployments involving HTTP/1.1 connection reuse, proxies, gateways, or load balancers, this malformed serialized request may also contribute to request smuggling or cache poisoning, depending on how downstream components parse the request.

Patches

The issue is patched in 2.10.2 and later. 1.x is end-of-life and will not receive a patch.

Workarounds

If you cannot upgrade immediately, validate and reject all untrusted URI strings before constructing PSR-7 Uri or Request instances. Reject input containing ASCII control characters, whitespace, or DEL, including CRLF, tab, space, NUL, or DEL characters:

if (preg_match('/[\x00-\x20\x7F]/', $untrustedUrl)) {
    throw new \InvalidArgumentException('Insecure URL detected');
}

Applications that manually serialize or forward requests should also ensure the final HTTP client, transport, or serializer rejects invalid URI and header data before writing requests to the network.

References

• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.2
• https://www.rfc-editor.org/rfc/rfc9112.html#section-5
• https://www.rfc-editor.org/rfc/rfc9112.html#section-11.2
• https://www.rfc-editor.org/rfc/rfc9110.html#section-7.2

Impact

guzzlehttp/psr7 did not reject URI host components containing authority delimiters (/, ?, #, @, or \), an embedded port such as host:8080, or IPv6 brackets that do not frame the host (such as [::1 or ::1]). Uri::assertValidHost() rejected only control characters, so these malformed hosts were accepted both when parsing a URI string — including through new Uri(), an absolute-form request target passed to Message::parseRequest(), and the synthetic SERVER_NAME or SERVER_ADDR fallback used by ServerRequest::fromGlobals() — and when setting a host with Uri::withHost(). Because the stored host was not validated, Uri::getHost() could return a value that does not agree with the URI's authority or with the host that is actually used on the wire. For example, Uri::withHost('good.com@evil.com') is accepted, and new Uri('http://[gggg::1]/') produces a getHost() of '[gggg:' while getAuthority() returns '[gggg::1'.

You are affected if your application builds a Uri or calls Uri::withHost() with host data that is wholly or partly attacker-controlled and then relies on Uri::getHost() for a security or routing decision, such as host allowlisting or denylisting, an SSRF guard, cookie scoping, or proxy-bypass selection. You are also affected if you parse, forward, proxy, or re-serialize URIs that come from untrusted raw HTTP messages or from synthetic $_SERVER values. Because getHost() can then disagree with the real connection target, the concrete impact depends on how your application and any downstream HTTP/1.x component use the URI, and may include host-based access-control bypass, server-side request forgery, routing to an unintended host, or Host header confusion. You are not affected if every host you place into a Uri is already trusted and well formed.

Applications using guzzlehttp/guzzle are affected in the same way through Guzzle's use of PSR-7. Guzzle derives the request Host header from the request URI, and its cookie matching and no_proxy proxy-bypass matching both read Uri::getHost(). An application that builds a Guzzle request URI from attacker-controlled host input can therefore have its Host header, cookie scope, or proxy-bypass decision computed against a host that differs from the one Guzzle connects to. This is not the normal request-sending path, and an application that passes only trusted, well-formed URIs to Guzzle and never builds a request URI from attacker-controlled host input is not affected through Guzzle's standard client APIs.

Patches

The issue is patched in 2.12.3 and later. Starting in that release, guzzlehttp/psr7 rejects URI host components that contain authority delimiters, an embedded port, or IPv6 brackets that do not frame the host, both when parsing a URI and via Uri::withHost(), so Uri::getHost() agrees with the URI authority. A framed bracketed literal whose contents are not a valid IPv6 address is preserved rather than rejected, so getHost() still agrees with the authority.

Workarounds

If you cannot upgrade immediately, validate and normalize host values before you build or modify a Uri from untrusted input, and do not treat Uri::getHost() as a trust boundary for a host you have not independently checked. Before passing a host to Uri, reject any value that contains /, ?, #, @, or \, that contains a colon outside a bracketed IPv6 literal, or that has unbalanced brackets. Applications that parse, forward, replay, or re-serialize raw HTTP messages, or that run with attacker-controlled $_SERVER values, should validate the host before calling Message::parseRequest() or ServerRequest::fromGlobals(), and should avoid reparsing untrusted input.

References

• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.3
• https://datatracker.ietf.org/doc/html/rfc6265#section-5.1.3

Impact

guzzlehttp/psr7 did not reject CR/LF characters in certain first-party HTTP start-line fields: the request method, protocol version, and response reason phrase. If an application placed attacker-controlled data into one of those fields and later serialized the PSR-7 message as raw HTTP/1.x, for example with Message::toString() or an equivalent serializer, the serialized message could contain attacker-controlled header lines. The issue can also be reached through Message::parseRequest() or Message::parseResponse() when malformed raw messages are parsed into first-party PSR-7 objects and then serialized again.

Creating or modifying a Request, Response, or other PSR-7 object alone is not sufficient. The issue requires the malformed message to be serialized and written to the network, forwarded, replayed, or otherwise processed by software that does not independently reject the malformed start line. This is not the normal request-sending path used by guzzlehttp/guzzle; applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected.

Applications are most likely to be affected when they manually serialize PSR-7 messages, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, testing, or similar code. Depending on how downstream HTTP/1.1 components parse the serialized message, this may lead to header injection, response splitting, request smuggling, or cache poisoning.

Patches

The issue is patched in 2.12.1 and later. Starting in that release, guzzlehttp/psr7 rejects CR/LF characters in HTTP method, protocol version, and response reason phrase values before storing them in first-party message objects.

Workarounds

If you cannot upgrade immediately, reject CR/LF in untrusted method, protocol version, and reason phrase values before constructing or modifying PSR-7 messages.

Applications that parse, forward, replay, or serialize raw HTTP messages cannot work around the parser entry points by validating only after parsing. They should validate the raw start line before calling Message::parseRequest() or Message::parseResponse(), avoid reparsing untrusted raw messages, or upgrade. If an application runs with attacker-controlled synthetic $_SERVER values, validate REQUEST_METHOD and SERVER_PROTOCOL before calling ServerRequest::fromGlobals().

Impact

guzzlehttp/psr7 improperly interpreted malformed Host header values when constructing request URIs from inbound request data. This issue concerns inbound request parsing and server request construction. It does not require serializing a PSR-7 request, and it is not part of the normal outbound request-sending path used by guzzlehttp/guzzle.

A vulnerable flow is:

1. An attacker controls a raw HTTP request or server variable containing a Host value.
2. The Host value contains URI authority delimiters, such as trusted.example@evil.example.
3. guzzlehttp/psr7 uses that value to construct a URI.
4. The URI parser treats the portion before @ as userinfo and the portion after @ as the URI host.
5. The resulting PSR-7 request URI host differs from the original Host header value.

For example, Host: trusted.example@evil.example can result in a PSR-7 URI whose host is evil.example, while the original Host header value remains trusted.example@evil.example.

Applications are affected if they parse attacker-controlled raw HTTP requests with GuzzleHttp\Psr7\Message::parseRequest() or the legacy 1.x GuzzleHttp\Psr7\parse_request() function, or if they build server requests from attacker-controlled server variables with GuzzleHttp\Psr7\ServerRequest::fromGlobals() or GuzzleHttp\Psr7\ServerRequest::getUriFromGlobals(), and then rely on the resulting URI host for routing, allow-list checks, credential selection, or forwarding decisions. Applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected. In affected forwarding or gateway scenarios, this may cause requests or credentials to be sent to an unintended host.

Patches

The issue is patched in 2.10.2 and later. 1.x is end-of-life and will not receive a patch.

Workarounds

If you cannot upgrade immediately, validate Host values before passing untrusted request data to Message::parseRequest(), legacy 1.x parse_request(), ServerRequest::fromGlobals(), or ServerRequest::getUriFromGlobals().

Accept only uri-host [ ":" port ]. Reject values containing whitespace, control characters, userinfo (@), path (/ or \), query (?), fragment (#), malformed IP literals or bracket syntax, or invalid port syntax.

Do not validate Host by prefixing it with http:// and passing it to parse_url(), because that can reinterpret malformed values as URI userinfo and host.

References

• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.2
• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.3
• https://www.rfc-editor.org/rfc/rfc9110.html#section-4.2.4
• https://www.rfc-editor.org/rfc/rfc9110.html#section-7.2

Impact

guzzlehttp/psr7 did not reject ASCII control characters, whitespace, or DEL in first-party URI host components. The issue requires a PSR-7 request to be serialized into a raw HTTP/1.x message, for example with GuzzleHttp\Psr7\Message::toString() or an equivalent custom serializer. Creating a Uri, Request, or other PSR-7 object alone is not sufficient. The malformed host must be copied into the serialized Host header without further validation.

A vulnerable flow is:

1. An application accepts a user-controlled URL.
2. The URL is used to construct a PSR-7 Uri or Request.
3. The host component contains CRLF or another header-unsafe character.
4. The request is serialized into a raw HTTP/1.x message without an explicit Host header.
5. The host is copied into the serialized Host header.
6. The serialized request is written to the network or otherwise processed by software that does not independently reject the malformed host.

In that flow, an attacker can cause the serialized request to contain additional attacker-controlled header lines. For example, a host containing "\r\nX-Injected: yes" can cause the generated Host header to span multiple HTTP header lines.

This is not the normal request-sending path used by guzzlehttp/guzzle. Applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected. Applications are most likely to be affected when they manually serialize PSR-7 requests, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, or similar request-dispatch code that serializes requests without independently validating URI hosts and header data. In deployments involving HTTP/1.1 connection reuse, proxies, gateways, or load balancers, this malformed serialized request may also contribute to request smuggling or cache poisoning, depending on how downstream components parse the request.

Patches

The issue is patched in 2.10.2 and later. 1.x is end-of-life and will not receive a patch.

Workarounds

If you cannot upgrade immediately, validate and reject all untrusted URI strings before constructing PSR-7 Uri or Request instances. Reject input containing ASCII control characters, whitespace, or DEL, including CRLF, tab, space, NUL, or DEL characters:

if (preg_match('/[\x00-\x20\x7F]/', $untrustedUrl)) {
    throw new \InvalidArgumentException('Insecure URL detected');
}

Applications that manually serialize or forward requests should also ensure the final HTTP client, transport, or serializer rejects invalid URI and header data before writing requests to the network.

References

• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.2
• https://www.rfc-editor.org/rfc/rfc9112.html#section-5
• https://www.rfc-editor.org/rfc/rfc9112.html#section-11.2
• https://www.rfc-editor.org/rfc/rfc9110.html#section-7.2

Impact

guzzlehttp/psr7 did not reject URI host components containing authority delimiters (/, ?, #, @, or \), an embedded port such as host:8080, or IPv6 brackets that do not frame the host (such as [::1 or ::1]). Uri::assertValidHost() rejected only control characters, so these malformed hosts were accepted both when parsing a URI string — including through new Uri(), an absolute-form request target passed to Message::parseRequest(), and the synthetic SERVER_NAME or SERVER_ADDR fallback used by ServerRequest::fromGlobals() — and when setting a host with Uri::withHost(). Because the stored host was not validated, Uri::getHost() could return a value that does not agree with the URI's authority or with the host that is actually used on the wire. For example, Uri::withHost('good.com@evil.com') is accepted, and new Uri('http://[gggg::1]/') produces a getHost() of '[gggg:' while getAuthority() returns '[gggg::1'.

You are affected if your application builds a Uri or calls Uri::withHost() with host data that is wholly or partly attacker-controlled and then relies on Uri::getHost() for a security or routing decision, such as host allowlisting or denylisting, an SSRF guard, cookie scoping, or proxy-bypass selection. You are also affected if you parse, forward, proxy, or re-serialize URIs that come from untrusted raw HTTP messages or from synthetic $_SERVER values. Because getHost() can then disagree with the real connection target, the concrete impact depends on how your application and any downstream HTTP/1.x component use the URI, and may include host-based access-control bypass, server-side request forgery, routing to an unintended host, or Host header confusion. You are not affected if every host you place into a Uri is already trusted and well formed.

Applications using guzzlehttp/guzzle are affected in the same way through Guzzle's use of PSR-7. Guzzle derives the request Host header from the request URI, and its cookie matching and no_proxy proxy-bypass matching both read Uri::getHost(). An application that builds a Guzzle request URI from attacker-controlled host input can therefore have its Host header, cookie scope, or proxy-bypass decision computed against a host that differs from the one Guzzle connects to. This is not the normal request-sending path, and an application that passes only trusted, well-formed URIs to Guzzle and never builds a request URI from attacker-controlled host input is not affected through Guzzle's standard client APIs.

Patches

The issue is patched in 2.12.3 and later. Starting in that release, guzzlehttp/psr7 rejects URI host components that contain authority delimiters, an embedded port, or IPv6 brackets that do not frame the host, both when parsing a URI and via Uri::withHost(), so Uri::getHost() agrees with the URI authority. A framed bracketed literal whose contents are not a valid IPv6 address is preserved rather than rejected, so getHost() still agrees with the authority.

Workarounds

If you cannot upgrade immediately, validate and normalize host values before you build or modify a Uri from untrusted input, and do not treat Uri::getHost() as a trust boundary for a host you have not independently checked. Before passing a host to Uri, reject any value that contains /, ?, #, @, or \, that contains a colon outside a bracketed IPv6 literal, or that has unbalanced brackets. Applications that parse, forward, replay, or re-serialize raw HTTP messages, or that run with attacker-controlled $_SERVER values, should validate the host before calling Message::parseRequest() or ServerRequest::fromGlobals(), and should avoid reparsing untrusted input.

References

• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.3
• https://datatracker.ietf.org/doc/html/rfc6265#section-5.1.3

Impact

guzzlehttp/psr7 did not reject CR/LF characters in certain first-party HTTP start-line fields: the request method, protocol version, and response reason phrase. If an application placed attacker-controlled data into one of those fields and later serialized the PSR-7 message as raw HTTP/1.x, for example with Message::toString() or an equivalent serializer, the serialized message could contain attacker-controlled header lines. The issue can also be reached through Message::parseRequest() or Message::parseResponse() when malformed raw messages are parsed into first-party PSR-7 objects and then serialized again.

Creating or modifying a Request, Response, or other PSR-7 object alone is not sufficient. The issue requires the malformed message to be serialized and written to the network, forwarded, replayed, or otherwise processed by software that does not independently reject the malformed start line. This is not the normal request-sending path used by guzzlehttp/guzzle; applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected.

Applications are most likely to be affected when they manually serialize PSR-7 messages, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, testing, or similar code. Depending on how downstream HTTP/1.1 components parse the serialized message, this may lead to header injection, response splitting, request smuggling, or cache poisoning.

Patches

The issue is patched in 2.12.1 and later. Starting in that release, guzzlehttp/psr7 rejects CR/LF characters in HTTP method, protocol version, and response reason phrase values before storing them in first-party message objects.

Workarounds

If you cannot upgrade immediately, reject CR/LF in untrusted method, protocol version, and reason phrase values before constructing or modifying PSR-7 messages.

Applications that parse, forward, replay, or serialize raw HTTP messages cannot work around the parser entry points by validating only after parsing. They should validate the raw start line before calling Message::parseRequest() or Message::parseResponse(), avoid reparsing untrusted raw messages, or upgrade. If an application runs with attacker-controlled synthetic $_SERVER values, validate REQUEST_METHOD and SERVER_PROTOCOL before calling ServerRequest::fromGlobals().

Impact

guzzlehttp/psr7 improperly interpreted malformed Host header values when constructing request URIs from inbound request data. This issue concerns inbound request parsing and server request construction. It does not require serializing a PSR-7 request, and it is not part of the normal outbound request-sending path used by guzzlehttp/guzzle.

A vulnerable flow is:

1. An attacker controls a raw HTTP request or server variable containing a Host value.
2. The Host value contains URI authority delimiters, such as trusted.example@evil.example.
3. guzzlehttp/psr7 uses that value to construct a URI.
4. The URI parser treats the portion before @ as userinfo and the portion after @ as the URI host.
5. The resulting PSR-7 request URI host differs from the original Host header value.

For example, Host: trusted.example@evil.example can result in a PSR-7 URI whose host is evil.example, while the original Host header value remains trusted.example@evil.example.

Applications are affected if they parse attacker-controlled raw HTTP requests with GuzzleHttp\Psr7\Message::parseRequest() or the legacy 1.x GuzzleHttp\Psr7\parse_request() function, or if they build server requests from attacker-controlled server variables with GuzzleHttp\Psr7\ServerRequest::fromGlobals() or GuzzleHttp\Psr7\ServerRequest::getUriFromGlobals(), and then rely on the resulting URI host for routing, allow-list checks, credential selection, or forwarding decisions. Applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected. In affected forwarding or gateway scenarios, this may cause requests or credentials to be sent to an unintended host.

Patches

The issue is patched in 2.10.2 and later. 1.x is end-of-life and will not receive a patch.

Workarounds

If you cannot upgrade immediately, validate Host values before passing untrusted request data to Message::parseRequest(), legacy 1.x parse_request(), ServerRequest::fromGlobals(), or ServerRequest::getUriFromGlobals().

Accept only uri-host [ ":" port ]. Reject values containing whitespace, control characters, userinfo (@), path (/ or \), query (?), fragment (#), malformed IP literals or bracket syntax, or invalid port syntax.

Do not validate Host by prefixing it with http:// and passing it to parse_url(), because that can reinterpret malformed values as URI userinfo and host.

References

• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.2
• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.3
• https://www.rfc-editor.org/rfc/rfc9110.html#section-4.2.4
• https://www.rfc-editor.org/rfc/rfc9110.html#section-7.2

Impact

guzzlehttp/psr7 did not reject ASCII control characters, whitespace, or DEL in first-party URI host components. The issue requires a PSR-7 request to be serialized into a raw HTTP/1.x message, for example with GuzzleHttp\Psr7\Message::toString() or an equivalent custom serializer. Creating a Uri, Request, or other PSR-7 object alone is not sufficient. The malformed host must be copied into the serialized Host header without further validation.

A vulnerable flow is:

1. An application accepts a user-controlled URL.
2. The URL is used to construct a PSR-7 Uri or Request.
3. The host component contains CRLF or another header-unsafe character.
4. The request is serialized into a raw HTTP/1.x message without an explicit Host header.
5. The host is copied into the serialized Host header.
6. The serialized request is written to the network or otherwise processed by software that does not independently reject the malformed host.

In that flow, an attacker can cause the serialized request to contain additional attacker-controlled header lines. For example, a host containing "\r\nX-Injected: yes" can cause the generated Host header to span multiple HTTP header lines.

This is not the normal request-sending path used by guzzlehttp/guzzle. Applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected. Applications are most likely to be affected when they manually serialize PSR-7 requests, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, or similar request-dispatch code that serializes requests without independently validating URI hosts and header data. In deployments involving HTTP/1.1 connection reuse, proxies, gateways, or load balancers, this malformed serialized request may also contribute to request smuggling or cache poisoning, depending on how downstream components parse the request.

Patches

The issue is patched in 2.10.2 and later. 1.x is end-of-life and will not receive a patch.

Workarounds

If you cannot upgrade immediately, validate and reject all untrusted URI strings before constructing PSR-7 Uri or Request instances. Reject input containing ASCII control characters, whitespace, or DEL, including CRLF, tab, space, NUL, or DEL characters:

if (preg_match('/[\x00-\x20\x7F]/', $untrustedUrl)) {
    throw new \InvalidArgumentException('Insecure URL detected');
}

Applications that manually serialize or forward requests should also ensure the final HTTP client, transport, or serializer rejects invalid URI and header data before writing requests to the network.

References

• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.2
• https://www.rfc-editor.org/rfc/rfc9112.html#section-5
• https://www.rfc-editor.org/rfc/rfc9112.html#section-11.2
• https://www.rfc-editor.org/rfc/rfc9110.html#section-7.2

Impact

guzzlehttp/psr7 did not reject URI host components containing authority delimiters (/, ?, #, @, or \), an embedded port such as host:8080, or IPv6 brackets that do not frame the host (such as [::1 or ::1]). Uri::assertValidHost() rejected only control characters, so these malformed hosts were accepted both when parsing a URI string — including through new Uri(), an absolute-form request target passed to Message::parseRequest(), and the synthetic SERVER_NAME or SERVER_ADDR fallback used by ServerRequest::fromGlobals() — and when setting a host with Uri::withHost(). Because the stored host was not validated, Uri::getHost() could return a value that does not agree with the URI's authority or with the host that is actually used on the wire. For example, Uri::withHost('good.com@evil.com') is accepted, and new Uri('http://[gggg::1]/') produces a getHost() of '[gggg:' while getAuthority() returns '[gggg::1'.

You are affected if your application builds a Uri or calls Uri::withHost() with host data that is wholly or partly attacker-controlled and then relies on Uri::getHost() for a security or routing decision, such as host allowlisting or denylisting, an SSRF guard, cookie scoping, or proxy-bypass selection. You are also affected if you parse, forward, proxy, or re-serialize URIs that come from untrusted raw HTTP messages or from synthetic $_SERVER values. Because getHost() can then disagree with the real connection target, the concrete impact depends on how your application and any downstream HTTP/1.x component use the URI, and may include host-based access-control bypass, server-side request forgery, routing to an unintended host, or Host header confusion. You are not affected if every host you place into a Uri is already trusted and well formed.

Applications using guzzlehttp/guzzle are affected in the same way through Guzzle's use of PSR-7. Guzzle derives the request Host header from the request URI, and its cookie matching and no_proxy proxy-bypass matching both read Uri::getHost(). An application that builds a Guzzle request URI from attacker-controlled host input can therefore have its Host header, cookie scope, or proxy-bypass decision computed against a host that differs from the one Guzzle connects to. This is not the normal request-sending path, and an application that passes only trusted, well-formed URIs to Guzzle and never builds a request URI from attacker-controlled host input is not affected through Guzzle's standard client APIs.

Patches

The issue is patched in 2.12.3 and later. Starting in that release, guzzlehttp/psr7 rejects URI host components that contain authority delimiters, an embedded port, or IPv6 brackets that do not frame the host, both when parsing a URI and via Uri::withHost(), so Uri::getHost() agrees with the URI authority. A framed bracketed literal whose contents are not a valid IPv6 address is preserved rather than rejected, so getHost() still agrees with the authority.

Workarounds

If you cannot upgrade immediately, validate and normalize host values before you build or modify a Uri from untrusted input, and do not treat Uri::getHost() as a trust boundary for a host you have not independently checked. Before passing a host to Uri, reject any value that contains /, ?, #, @, or \, that contains a colon outside a bracketed IPv6 literal, or that has unbalanced brackets. Applications that parse, forward, replay, or re-serialize raw HTTP messages, or that run with attacker-controlled $_SERVER values, should validate the host before calling Message::parseRequest() or ServerRequest::fromGlobals(), and should avoid reparsing untrusted input.

References

• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.3
• https://datatracker.ietf.org/doc/html/rfc6265#section-5.1.3

Impact

guzzlehttp/psr7 did not reject CR/LF characters in certain first-party HTTP start-line fields: the request method, protocol version, and response reason phrase. If an application placed attacker-controlled data into one of those fields and later serialized the PSR-7 message as raw HTTP/1.x, for example with Message::toString() or an equivalent serializer, the serialized message could contain attacker-controlled header lines. The issue can also be reached through Message::parseRequest() or Message::parseResponse() when malformed raw messages are parsed into first-party PSR-7 objects and then serialized again.

Creating or modifying a Request, Response, or other PSR-7 object alone is not sufficient. The issue requires the malformed message to be serialized and written to the network, forwarded, replayed, or otherwise processed by software that does not independently reject the malformed start line. This is not the normal request-sending path used by guzzlehttp/guzzle; applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected.

Applications are most likely to be affected when they manually serialize PSR-7 messages, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, testing, or similar code. Depending on how downstream HTTP/1.1 components parse the serialized message, this may lead to header injection, response splitting, request smuggling, or cache poisoning.

Patches

The issue is patched in 2.12.1 and later. Starting in that release, guzzlehttp/psr7 rejects CR/LF characters in HTTP method, protocol version, and response reason phrase values before storing them in first-party message objects.

Workarounds

If you cannot upgrade immediately, reject CR/LF in untrusted method, protocol version, and reason phrase values before constructing or modifying PSR-7 messages.

Applications that parse, forward, replay, or serialize raw HTTP messages cannot work around the parser entry points by validating only after parsing. They should validate the raw start line before calling Message::parseRequest() or Message::parseResponse(), avoid reparsing untrusted raw messages, or upgrade. If an application runs with attacker-controlled synthetic $_SERVER values, validate REQUEST_METHOD and SERVER_PROTOCOL before calling ServerRequest::fromGlobals().

Impact

guzzlehttp/psr7 improperly interpreted malformed Host header values when constructing request URIs from inbound request data. This issue concerns inbound request parsing and server request construction. It does not require serializing a PSR-7 request, and it is not part of the normal outbound request-sending path used by guzzlehttp/guzzle.

A vulnerable flow is:

1. An attacker controls a raw HTTP request or server variable containing a Host value.
2. The Host value contains URI authority delimiters, such as trusted.example@evil.example.
3. guzzlehttp/psr7 uses that value to construct a URI.
4. The URI parser treats the portion before @ as userinfo and the portion after @ as the URI host.
5. The resulting PSR-7 request URI host differs from the original Host header value.

For example, Host: trusted.example@evil.example can result in a PSR-7 URI whose host is evil.example, while the original Host header value remains trusted.example@evil.example.

Applications are affected if they parse attacker-controlled raw HTTP requests with GuzzleHttp\Psr7\Message::parseRequest() or the legacy 1.x GuzzleHttp\Psr7\parse_request() function, or if they build server requests from attacker-controlled server variables with GuzzleHttp\Psr7\ServerRequest::fromGlobals() or GuzzleHttp\Psr7\ServerRequest::getUriFromGlobals(), and then rely on the resulting URI host for routing, allow-list checks, credential selection, or forwarding decisions. Applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected. In affected forwarding or gateway scenarios, this may cause requests or credentials to be sent to an unintended host.

Patches

The issue is patched in 2.10.2 and later. 1.x is end-of-life and will not receive a patch.

Workarounds

If you cannot upgrade immediately, validate Host values before passing untrusted request data to Message::parseRequest(), legacy 1.x parse_request(), ServerRequest::fromGlobals(), or ServerRequest::getUriFromGlobals().

Accept only uri-host [ ":" port ]. Reject values containing whitespace, control characters, userinfo (@), path (/ or \), query (?), fragment (#), malformed IP literals or bracket syntax, or invalid port syntax.

Do not validate Host by prefixing it with http:// and passing it to parse_url(), because that can reinterpret malformed values as URI userinfo and host.

References

• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.2
• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.3
• https://www.rfc-editor.org/rfc/rfc9110.html#section-4.2.4
• https://www.rfc-editor.org/rfc/rfc9110.html#section-7.2

Impact

guzzlehttp/psr7 did not reject ASCII control characters, whitespace, or DEL in first-party URI host components. The issue requires a PSR-7 request to be serialized into a raw HTTP/1.x message, for example with GuzzleHttp\Psr7\Message::toString() or an equivalent custom serializer. Creating a Uri, Request, or other PSR-7 object alone is not sufficient. The malformed host must be copied into the serialized Host header without further validation.

A vulnerable flow is:

1. An application accepts a user-controlled URL.
2. The URL is used to construct a PSR-7 Uri or Request.
3. The host component contains CRLF or another header-unsafe character.
4. The request is serialized into a raw HTTP/1.x message without an explicit Host header.
5. The host is copied into the serialized Host header.
6. The serialized request is written to the network or otherwise processed by software that does not independently reject the malformed host.

In that flow, an attacker can cause the serialized request to contain additional attacker-controlled header lines. For example, a host containing "\r\nX-Injected: yes" can cause the generated Host header to span multiple HTTP header lines.

This is not the normal request-sending path used by guzzlehttp/guzzle. Applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected. Applications are most likely to be affected when they manually serialize PSR-7 requests, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, or similar request-dispatch code that serializes requests without independently validating URI hosts and header data. In deployments involving HTTP/1.1 connection reuse, proxies, gateways, or load balancers, this malformed serialized request may also contribute to request smuggling or cache poisoning, depending on how downstream components parse the request.

Patches

The issue is patched in 2.10.2 and later. 1.x is end-of-life and will not receive a patch.

Workarounds

If you cannot upgrade immediately, validate and reject all untrusted URI strings before constructing PSR-7 Uri or Request instances. Reject input containing ASCII control characters, whitespace, or DEL, including CRLF, tab, space, NUL, or DEL characters:

if (preg_match('/[\x00-\x20\x7F]/', $untrustedUrl)) {
    throw new \InvalidArgumentException('Insecure URL detected');
}

Applications that manually serialize or forward requests should also ensure the final HTTP client, transport, or serializer rejects invalid URI and header data before writing requests to the network.

References

• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.2
• https://www.rfc-editor.org/rfc/rfc9112.html#section-5
• https://www.rfc-editor.org/rfc/rfc9112.html#section-11.2
• https://www.rfc-editor.org/rfc/rfc9110.html#section-7.2

Impact

guzzlehttp/psr7 did not reject URI host components containing authority delimiters (/, ?, #, @, or \), an embedded port such as host:8080, or IPv6 brackets that do not frame the host (such as [::1 or ::1]). Uri::assertValidHost() rejected only control characters, so these malformed hosts were accepted both when parsing a URI string — including through new Uri(), an absolute-form request target passed to Message::parseRequest(), and the synthetic SERVER_NAME or SERVER_ADDR fallback used by ServerRequest::fromGlobals() — and when setting a host with Uri::withHost(). Because the stored host was not validated, Uri::getHost() could return a value that does not agree with the URI's authority or with the host that is actually used on the wire. For example, Uri::withHost('good.com@evil.com') is accepted, and new Uri('http://[gggg::1]/') produces a getHost() of '[gggg:' while getAuthority() returns '[gggg::1'.

You are affected if your application builds a Uri or calls Uri::withHost() with host data that is wholly or partly attacker-controlled and then relies on Uri::getHost() for a security or routing decision, such as host allowlisting or denylisting, an SSRF guard, cookie scoping, or proxy-bypass selection. You are also affected if you parse, forward, proxy, or re-serialize URIs that come from untrusted raw HTTP messages or from synthetic $_SERVER values. Because getHost() can then disagree with the real connection target, the concrete impact depends on how your application and any downstream HTTP/1.x component use the URI, and may include host-based access-control bypass, server-side request forgery, routing to an unintended host, or Host header confusion. You are not affected if every host you place into a Uri is already trusted and well formed.

Applications using guzzlehttp/guzzle are affected in the same way through Guzzle's use of PSR-7. Guzzle derives the request Host header from the request URI, and its cookie matching and no_proxy proxy-bypass matching both read Uri::getHost(). An application that builds a Guzzle request URI from attacker-controlled host input can therefore have its Host header, cookie scope, or proxy-bypass decision computed against a host that differs from the one Guzzle connects to. This is not the normal request-sending path, and an application that passes only trusted, well-formed URIs to Guzzle and never builds a request URI from attacker-controlled host input is not affected through Guzzle's standard client APIs.

Patches

The issue is patched in 2.12.3 and later. Starting in that release, guzzlehttp/psr7 rejects URI host components that contain authority delimiters, an embedded port, or IPv6 brackets that do not frame the host, both when parsing a URI and via Uri::withHost(), so Uri::getHost() agrees with the URI authority. A framed bracketed literal whose contents are not a valid IPv6 address is preserved rather than rejected, so getHost() still agrees with the authority.

Workarounds

If you cannot upgrade immediately, validate and normalize host values before you build or modify a Uri from untrusted input, and do not treat Uri::getHost() as a trust boundary for a host you have not independently checked. Before passing a host to Uri, reject any value that contains /, ?, #, @, or \, that contains a colon outside a bracketed IPv6 literal, or that has unbalanced brackets. Applications that parse, forward, replay, or re-serialize raw HTTP messages, or that run with attacker-controlled $_SERVER values, should validate the host before calling Message::parseRequest() or ServerRequest::fromGlobals(), and should avoid reparsing untrusted input.

References

• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.3
• https://datatracker.ietf.org/doc/html/rfc6265#section-5.1.3

Impact

guzzlehttp/psr7 did not reject CR/LF characters in certain first-party HTTP start-line fields: the request method, protocol version, and response reason phrase. If an application placed attacker-controlled data into one of those fields and later serialized the PSR-7 message as raw HTTP/1.x, for example with Message::toString() or an equivalent serializer, the serialized message could contain attacker-controlled header lines. The issue can also be reached through Message::parseRequest() or Message::parseResponse() when malformed raw messages are parsed into first-party PSR-7 objects and then serialized again.

Creating or modifying a Request, Response, or other PSR-7 object alone is not sufficient. The issue requires the malformed message to be serialized and written to the network, forwarded, replayed, or otherwise processed by software that does not independently reject the malformed start line. This is not the normal request-sending path used by guzzlehttp/guzzle; applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected.

Applications are most likely to be affected when they manually serialize PSR-7 messages, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, testing, or similar code. Depending on how downstream HTTP/1.1 components parse the serialized message, this may lead to header injection, response splitting, request smuggling, or cache poisoning.

Patches

The issue is patched in 2.12.1 and later. Starting in that release, guzzlehttp/psr7 rejects CR/LF characters in HTTP method, protocol version, and response reason phrase values before storing them in first-party message objects.

Workarounds

If you cannot upgrade immediately, reject CR/LF in untrusted method, protocol version, and reason phrase values before constructing or modifying PSR-7 messages.

Applications that parse, forward, replay, or serialize raw HTTP messages cannot work around the parser entry points by validating only after parsing. They should validate the raw start line before calling Message::parseRequest() or Message::parseResponse(), avoid reparsing untrusted raw messages, or upgrade. If an application runs with attacker-controlled synthetic $_SERVER values, validate REQUEST_METHOD and SERVER_PROTOCOL before calling ServerRequest::fromGlobals().

Impact

guzzlehttp/psr7 improperly interpreted malformed Host header values when constructing request URIs from inbound request data. This issue concerns inbound request parsing and server request construction. It does not require serializing a PSR-7 request, and it is not part of the normal outbound request-sending path used by guzzlehttp/guzzle.

A vulnerable flow is:

1. An attacker controls a raw HTTP request or server variable containing a Host value.
2. The Host value contains URI authority delimiters, such as trusted.example@evil.example.
3. guzzlehttp/psr7 uses that value to construct a URI.
4. The URI parser treats the portion before @ as userinfo and the portion after @ as the URI host.
5. The resulting PSR-7 request URI host differs from the original Host header value.

For example, Host: trusted.example@evil.example can result in a PSR-7 URI whose host is evil.example, while the original Host header value remains trusted.example@evil.example.

Applications are affected if they parse attacker-controlled raw HTTP requests with GuzzleHttp\Psr7\Message::parseRequest() or the legacy 1.x GuzzleHttp\Psr7\parse_request() function, or if they build server requests from attacker-controlled server variables with GuzzleHttp\Psr7\ServerRequest::fromGlobals() or GuzzleHttp\Psr7\ServerRequest::getUriFromGlobals(), and then rely on the resulting URI host for routing, allow-list checks, credential selection, or forwarding decisions. Applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected. In affected forwarding or gateway scenarios, this may cause requests or credentials to be sent to an unintended host.

Patches

The issue is patched in 2.10.2 and later. 1.x is end-of-life and will not receive a patch.

Workarounds

If you cannot upgrade immediately, validate Host values before passing untrusted request data to Message::parseRequest(), legacy 1.x parse_request(), ServerRequest::fromGlobals(), or ServerRequest::getUriFromGlobals().

Accept only uri-host [ ":" port ]. Reject values containing whitespace, control characters, userinfo (@), path (/ or \), query (?), fragment (#), malformed IP literals or bracket syntax, or invalid port syntax.

Do not validate Host by prefixing it with http:// and passing it to parse_url(), because that can reinterpret malformed values as URI userinfo and host.

References

• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.2
• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.3
• https://www.rfc-editor.org/rfc/rfc9110.html#section-4.2.4
• https://www.rfc-editor.org/rfc/rfc9110.html#section-7.2

Impact

guzzlehttp/psr7 did not reject ASCII control characters, whitespace, or DEL in first-party URI host components. The issue requires a PSR-7 request to be serialized into a raw HTTP/1.x message, for example with GuzzleHttp\Psr7\Message::toString() or an equivalent custom serializer. Creating a Uri, Request, or other PSR-7 object alone is not sufficient. The malformed host must be copied into the serialized Host header without further validation.

A vulnerable flow is:

1. An application accepts a user-controlled URL.
2. The URL is used to construct a PSR-7 Uri or Request.
3. The host component contains CRLF or another header-unsafe character.
4. The request is serialized into a raw HTTP/1.x message without an explicit Host header.
5. The host is copied into the serialized Host header.
6. The serialized request is written to the network or otherwise processed by software that does not independently reject the malformed host.

In that flow, an attacker can cause the serialized request to contain additional attacker-controlled header lines. For example, a host containing "\r\nX-Injected: yes" can cause the generated Host header to span multiple HTTP header lines.

This is not the normal request-sending path used by guzzlehttp/guzzle. Applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected. Applications are most likely to be affected when they manually serialize PSR-7 requests, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, or similar request-dispatch code that serializes requests without independently validating URI hosts and header data. In deployments involving HTTP/1.1 connection reuse, proxies, gateways, or load balancers, this malformed serialized request may also contribute to request smuggling or cache poisoning, depending on how downstream components parse the request.

Patches

The issue is patched in 2.10.2 and later. 1.x is end-of-life and will not receive a patch.

Workarounds

If you cannot upgrade immediately, validate and reject all untrusted URI strings before constructing PSR-7 Uri or Request instances. Reject input containing ASCII control characters, whitespace, or DEL, including CRLF, tab, space, NUL, or DEL characters:

if (preg_match('/[\x00-\x20\x7F]/', $untrustedUrl)) {
    throw new \InvalidArgumentException('Insecure URL detected');
}

Applications that manually serialize or forward requests should also ensure the final HTTP client, transport, or serializer rejects invalid URI and header data before writing requests to the network.

References

• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.2
• https://www.rfc-editor.org/rfc/rfc9112.html#section-5
• https://www.rfc-editor.org/rfc/rfc9112.html#section-11.2
• https://www.rfc-editor.org/rfc/rfc9110.html#section-7.2

Impact

guzzlehttp/psr7 did not reject URI host components containing authority delimiters (/, ?, #, @, or \), an embedded port such as host:8080, or IPv6 brackets that do not frame the host (such as [::1 or ::1]). Uri::assertValidHost() rejected only control characters, so these malformed hosts were accepted both when parsing a URI string — including through new Uri(), an absolute-form request target passed to Message::parseRequest(), and the synthetic SERVER_NAME or SERVER_ADDR fallback used by ServerRequest::fromGlobals() — and when setting a host with Uri::withHost(). Because the stored host was not validated, Uri::getHost() could return a value that does not agree with the URI's authority or with the host that is actually used on the wire. For example, Uri::withHost('good.com@evil.com') is accepted, and new Uri('http://[gggg::1]/') produces a getHost() of '[gggg:' while getAuthority() returns '[gggg::1'.

You are affected if your application builds a Uri or calls Uri::withHost() with host data that is wholly or partly attacker-controlled and then relies on Uri::getHost() for a security or routing decision, such as host allowlisting or denylisting, an SSRF guard, cookie scoping, or proxy-bypass selection. You are also affected if you parse, forward, proxy, or re-serialize URIs that come from untrusted raw HTTP messages or from synthetic $_SERVER values. Because getHost() can then disagree with the real connection target, the concrete impact depends on how your application and any downstream HTTP/1.x component use the URI, and may include host-based access-control bypass, server-side request forgery, routing to an unintended host, or Host header confusion. You are not affected if every host you place into a Uri is already trusted and well formed.

Applications using guzzlehttp/guzzle are affected in the same way through Guzzle's use of PSR-7. Guzzle derives the request Host header from the request URI, and its cookie matching and no_proxy proxy-bypass matching both read Uri::getHost(). An application that builds a Guzzle request URI from attacker-controlled host input can therefore have its Host header, cookie scope, or proxy-bypass decision computed against a host that differs from the one Guzzle connects to. This is not the normal request-sending path, and an application that passes only trusted, well-formed URIs to Guzzle and never builds a request URI from attacker-controlled host input is not affected through Guzzle's standard client APIs.

Patches

The issue is patched in 2.12.3 and later. Starting in that release, guzzlehttp/psr7 rejects URI host components that contain authority delimiters, an embedded port, or IPv6 brackets that do not frame the host, both when parsing a URI and via Uri::withHost(), so Uri::getHost() agrees with the URI authority. A framed bracketed literal whose contents are not a valid IPv6 address is preserved rather than rejected, so getHost() still agrees with the authority.

Workarounds

If you cannot upgrade immediately, validate and normalize host values before you build or modify a Uri from untrusted input, and do not treat Uri::getHost() as a trust boundary for a host you have not independently checked. Before passing a host to Uri, reject any value that contains /, ?, #, @, or \, that contains a colon outside a bracketed IPv6 literal, or that has unbalanced brackets. Applications that parse, forward, replay, or re-serialize raw HTTP messages, or that run with attacker-controlled $_SERVER values, should validate the host before calling Message::parseRequest() or ServerRequest::fromGlobals(), and should avoid reparsing untrusted input.

References

• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.3
• https://datatracker.ietf.org/doc/html/rfc6265#section-5.1.3

Impact

guzzlehttp/psr7 did not reject CR/LF characters in certain first-party HTTP start-line fields: the request method, protocol version, and response reason phrase. If an application placed attacker-controlled data into one of those fields and later serialized the PSR-7 message as raw HTTP/1.x, for example with Message::toString() or an equivalent serializer, the serialized message could contain attacker-controlled header lines. The issue can also be reached through Message::parseRequest() or Message::parseResponse() when malformed raw messages are parsed into first-party PSR-7 objects and then serialized again.

Creating or modifying a Request, Response, or other PSR-7 object alone is not sufficient. The issue requires the malformed message to be serialized and written to the network, forwarded, replayed, or otherwise processed by software that does not independently reject the malformed start line. This is not the normal request-sending path used by guzzlehttp/guzzle; applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected.

Applications are most likely to be affected when they manually serialize PSR-7 messages, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, testing, or similar code. Depending on how downstream HTTP/1.1 components parse the serialized message, this may lead to header injection, response splitting, request smuggling, or cache poisoning.

Patches

The issue is patched in 2.12.1 and later. Starting in that release, guzzlehttp/psr7 rejects CR/LF characters in HTTP method, protocol version, and response reason phrase values before storing them in first-party message objects.

Workarounds

If you cannot upgrade immediately, reject CR/LF in untrusted method, protocol version, and reason phrase values before constructing or modifying PSR-7 messages.

Applications that parse, forward, replay, or serialize raw HTTP messages cannot work around the parser entry points by validating only after parsing. They should validate the raw start line before calling Message::parseRequest() or Message::parseResponse(), avoid reparsing untrusted raw messages, or upgrade. If an application runs with attacker-controlled synthetic $_SERVER values, validate REQUEST_METHOD and SERVER_PROTOCOL before calling ServerRequest::fromGlobals().

Impact

guzzlehttp/psr7 improperly interpreted malformed Host header values when constructing request URIs from inbound request data. This issue concerns inbound request parsing and server request construction. It does not require serializing a PSR-7 request, and it is not part of the normal outbound request-sending path used by guzzlehttp/guzzle.

A vulnerable flow is:

1. An attacker controls a raw HTTP request or server variable containing a Host value.
2. The Host value contains URI authority delimiters, such as trusted.example@evil.example.
3. guzzlehttp/psr7 uses that value to construct a URI.
4. The URI parser treats the portion before @ as userinfo and the portion after @ as the URI host.
5. The resulting PSR-7 request URI host differs from the original Host header value.

For example, Host: trusted.example@evil.example can result in a PSR-7 URI whose host is evil.example, while the original Host header value remains trusted.example@evil.example.

Applications are affected if they parse attacker-controlled raw HTTP requests with GuzzleHttp\Psr7\Message::parseRequest() or the legacy 1.x GuzzleHttp\Psr7\parse_request() function, or if they build server requests from attacker-controlled server variables with GuzzleHttp\Psr7\ServerRequest::fromGlobals() or GuzzleHttp\Psr7\ServerRequest::getUriFromGlobals(), and then rely on the resulting URI host for routing, allow-list checks, credential selection, or forwarding decisions. Applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected. In affected forwarding or gateway scenarios, this may cause requests or credentials to be sent to an unintended host.

Patches

The issue is patched in 2.10.2 and later. 1.x is end-of-life and will not receive a patch.

Workarounds

If you cannot upgrade immediately, validate Host values before passing untrusted request data to Message::parseRequest(), legacy 1.x parse_request(), ServerRequest::fromGlobals(), or ServerRequest::getUriFromGlobals().

Accept only uri-host [ ":" port ]. Reject values containing whitespace, control characters, userinfo (@), path (/ or \), query (?), fragment (#), malformed IP literals or bracket syntax, or invalid port syntax.

Do not validate Host by prefixing it with http:// and passing it to parse_url(), because that can reinterpret malformed values as URI userinfo and host.

References

• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.2
• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.3
• https://www.rfc-editor.org/rfc/rfc9110.html#section-4.2.4
• https://www.rfc-editor.org/rfc/rfc9110.html#section-7.2

Impact

guzzlehttp/psr7 did not reject ASCII control characters, whitespace, or DEL in first-party URI host components. The issue requires a PSR-7 request to be serialized into a raw HTTP/1.x message, for example with GuzzleHttp\Psr7\Message::toString() or an equivalent custom serializer. Creating a Uri, Request, or other PSR-7 object alone is not sufficient. The malformed host must be copied into the serialized Host header without further validation.

A vulnerable flow is:

1. An application accepts a user-controlled URL.
2. The URL is used to construct a PSR-7 Uri or Request.
3. The host component contains CRLF or another header-unsafe character.
4. The request is serialized into a raw HTTP/1.x message without an explicit Host header.
5. The host is copied into the serialized Host header.
6. The serialized request is written to the network or otherwise processed by software that does not independently reject the malformed host.

In that flow, an attacker can cause the serialized request to contain additional attacker-controlled header lines. For example, a host containing "\r\nX-Injected: yes" can cause the generated Host header to span multiple HTTP header lines.

This is not the normal request-sending path used by guzzlehttp/guzzle. Applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected. Applications are most likely to be affected when they manually serialize PSR-7 requests, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, or similar request-dispatch code that serializes requests without independently validating URI hosts and header data. In deployments involving HTTP/1.1 connection reuse, proxies, gateways, or load balancers, this malformed serialized request may also contribute to request smuggling or cache poisoning, depending on how downstream components parse the request.

Patches

The issue is patched in 2.10.2 and later. 1.x is end-of-life and will not receive a patch.

Workarounds

If you cannot upgrade immediately, validate and reject all untrusted URI strings before constructing PSR-7 Uri or Request instances. Reject input containing ASCII control characters, whitespace, or DEL, including CRLF, tab, space, NUL, or DEL characters:

if (preg_match('/[\x00-\x20\x7F]/', $untrustedUrl)) {
    throw new \InvalidArgumentException('Insecure URL detected');
}

Applications that manually serialize or forward requests should also ensure the final HTTP client, transport, or serializer rejects invalid URI and header data before writing requests to the network.

References

• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.2
• https://www.rfc-editor.org/rfc/rfc9112.html#section-5
• https://www.rfc-editor.org/rfc/rfc9112.html#section-11.2
• https://www.rfc-editor.org/rfc/rfc9110.html#section-7.2

Impact

guzzlehttp/psr7 did not reject URI host components containing authority delimiters (/, ?, #, @, or \), an embedded port such as host:8080, or IPv6 brackets that do not frame the host (such as [::1 or ::1]). Uri::assertValidHost() rejected only control characters, so these malformed hosts were accepted both when parsing a URI string — including through new Uri(), an absolute-form request target passed to Message::parseRequest(), and the synthetic SERVER_NAME or SERVER_ADDR fallback used by ServerRequest::fromGlobals() — and when setting a host with Uri::withHost(). Because the stored host was not validated, Uri::getHost() could return a value that does not agree with the URI's authority or with the host that is actually used on the wire. For example, Uri::withHost('good.com@evil.com') is accepted, and new Uri('http://[gggg::1]/') produces a getHost() of '[gggg:' while getAuthority() returns '[gggg::1'.

You are affected if your application builds a Uri or calls Uri::withHost() with host data that is wholly or partly attacker-controlled and then relies on Uri::getHost() for a security or routing decision, such as host allowlisting or denylisting, an SSRF guard, cookie scoping, or proxy-bypass selection. You are also affected if you parse, forward, proxy, or re-serialize URIs that come from untrusted raw HTTP messages or from synthetic $_SERVER values. Because getHost() can then disagree with the real connection target, the concrete impact depends on how your application and any downstream HTTP/1.x component use the URI, and may include host-based access-control bypass, server-side request forgery, routing to an unintended host, or Host header confusion. You are not affected if every host you place into a Uri is already trusted and well formed.

Applications using guzzlehttp/guzzle are affected in the same way through Guzzle's use of PSR-7. Guzzle derives the request Host header from the request URI, and its cookie matching and no_proxy proxy-bypass matching both read Uri::getHost(). An application that builds a Guzzle request URI from attacker-controlled host input can therefore have its Host header, cookie scope, or proxy-bypass decision computed against a host that differs from the one Guzzle connects to. This is not the normal request-sending path, and an application that passes only trusted, well-formed URIs to Guzzle and never builds a request URI from attacker-controlled host input is not affected through Guzzle's standard client APIs.

Patches

The issue is patched in 2.12.3 and later. Starting in that release, guzzlehttp/psr7 rejects URI host components that contain authority delimiters, an embedded port, or IPv6 brackets that do not frame the host, both when parsing a URI and via Uri::withHost(), so Uri::getHost() agrees with the URI authority. A framed bracketed literal whose contents are not a valid IPv6 address is preserved rather than rejected, so getHost() still agrees with the authority.

Workarounds

If you cannot upgrade immediately, validate and normalize host values before you build or modify a Uri from untrusted input, and do not treat Uri::getHost() as a trust boundary for a host you have not independently checked. Before passing a host to Uri, reject any value that contains /, ?, #, @, or \, that contains a colon outside a bracketed IPv6 literal, or that has unbalanced brackets. Applications that parse, forward, replay, or re-serialize raw HTTP messages, or that run with attacker-controlled $_SERVER values, should validate the host before calling Message::parseRequest() or ServerRequest::fromGlobals(), and should avoid reparsing untrusted input.

References

• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.3
• https://datatracker.ietf.org/doc/html/rfc6265#section-5.1.3

Impact

guzzlehttp/psr7 did not reject CR/LF characters in certain first-party HTTP start-line fields: the request method, protocol version, and response reason phrase. If an application placed attacker-controlled data into one of those fields and later serialized the PSR-7 message as raw HTTP/1.x, for example with Message::toString() or an equivalent serializer, the serialized message could contain attacker-controlled header lines. The issue can also be reached through Message::parseRequest() or Message::parseResponse() when malformed raw messages are parsed into first-party PSR-7 objects and then serialized again.

Creating or modifying a Request, Response, or other PSR-7 object alone is not sufficient. The issue requires the malformed message to be serialized and written to the network, forwarded, replayed, or otherwise processed by software that does not independently reject the malformed start line. This is not the normal request-sending path used by guzzlehttp/guzzle; applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected.

Applications are most likely to be affected when they manually serialize PSR-7 messages, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, testing, or similar code. Depending on how downstream HTTP/1.1 components parse the serialized message, this may lead to header injection, response splitting, request smuggling, or cache poisoning.

Patches

The issue is patched in 2.12.1 and later. Starting in that release, guzzlehttp/psr7 rejects CR/LF characters in HTTP method, protocol version, and response reason phrase values before storing them in first-party message objects.

Workarounds

If you cannot upgrade immediately, reject CR/LF in untrusted method, protocol version, and reason phrase values before constructing or modifying PSR-7 messages.

Applications that parse, forward, replay, or serialize raw HTTP messages cannot work around the parser entry points by validating only after parsing. They should validate the raw start line before calling Message::parseRequest() or Message::parseResponse(), avoid reparsing untrusted raw messages, or upgrade. If an application runs with attacker-controlled synthetic $_SERVER values, validate REQUEST_METHOD and SERVER_PROTOCOL before calling ServerRequest::fromGlobals().

Impact

guzzlehttp/psr7 improperly interpreted malformed Host header values when constructing request URIs from inbound request data. This issue concerns inbound request parsing and server request construction. It does not require serializing a PSR-7 request, and it is not part of the normal outbound request-sending path used by guzzlehttp/guzzle.

A vulnerable flow is:

1. An attacker controls a raw HTTP request or server variable containing a Host value.
2. The Host value contains URI authority delimiters, such as trusted.example@evil.example.
3. guzzlehttp/psr7 uses that value to construct a URI.
4. The URI parser treats the portion before @ as userinfo and the portion after @ as the URI host.
5. The resulting PSR-7 request URI host differs from the original Host header value.

For example, Host: trusted.example@evil.example can result in a PSR-7 URI whose host is evil.example, while the original Host header value remains trusted.example@evil.example.

Applications are affected if they parse attacker-controlled raw HTTP requests with GuzzleHttp\Psr7\Message::parseRequest() or the legacy 1.x GuzzleHttp\Psr7\parse_request() function, or if they build server requests from attacker-controlled server variables with GuzzleHttp\Psr7\ServerRequest::fromGlobals() or GuzzleHttp\Psr7\ServerRequest::getUriFromGlobals(), and then rely on the resulting URI host for routing, allow-list checks, credential selection, or forwarding decisions. Applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected. In affected forwarding or gateway scenarios, this may cause requests or credentials to be sent to an unintended host.

Patches

The issue is patched in 2.10.2 and later. 1.x is end-of-life and will not receive a patch.

Workarounds

If you cannot upgrade immediately, validate Host values before passing untrusted request data to Message::parseRequest(), legacy 1.x parse_request(), ServerRequest::fromGlobals(), or ServerRequest::getUriFromGlobals().

Accept only uri-host [ ":" port ]. Reject values containing whitespace, control characters, userinfo (@), path (/ or \), query (?), fragment (#), malformed IP literals or bracket syntax, or invalid port syntax.

Do not validate Host by prefixing it with http:// and passing it to parse_url(), because that can reinterpret malformed values as URI userinfo and host.

References

• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.2
• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.3
• https://www.rfc-editor.org/rfc/rfc9110.html#section-4.2.4
• https://www.rfc-editor.org/rfc/rfc9110.html#section-7.2

Impact

guzzlehttp/psr7 did not reject ASCII control characters, whitespace, or DEL in first-party URI host components. The issue requires a PSR-7 request to be serialized into a raw HTTP/1.x message, for example with GuzzleHttp\Psr7\Message::toString() or an equivalent custom serializer. Creating a Uri, Request, or other PSR-7 object alone is not sufficient. The malformed host must be copied into the serialized Host header without further validation.

A vulnerable flow is:

1. An application accepts a user-controlled URL.
2. The URL is used to construct a PSR-7 Uri or Request.
3. The host component contains CRLF or another header-unsafe character.
4. The request is serialized into a raw HTTP/1.x message without an explicit Host header.
5. The host is copied into the serialized Host header.
6. The serialized request is written to the network or otherwise processed by software that does not independently reject the malformed host.

In that flow, an attacker can cause the serialized request to contain additional attacker-controlled header lines. For example, a host containing "\r\nX-Injected: yes" can cause the generated Host header to span multiple HTTP header lines.

This is not the normal request-sending path used by guzzlehttp/guzzle. Applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected. Applications are most likely to be affected when they manually serialize PSR-7 requests, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, or similar request-dispatch code that serializes requests without independently validating URI hosts and header data. In deployments involving HTTP/1.1 connection reuse, proxies, gateways, or load balancers, this malformed serialized request may also contribute to request smuggling or cache poisoning, depending on how downstream components parse the request.

Patches

The issue is patched in 2.10.2 and later. 1.x is end-of-life and will not receive a patch.

Workarounds

If you cannot upgrade immediately, validate and reject all untrusted URI strings before constructing PSR-7 Uri or Request instances. Reject input containing ASCII control characters, whitespace, or DEL, including CRLF, tab, space, NUL, or DEL characters:

if (preg_match('/[\x00-\x20\x7F]/', $untrustedUrl)) {
    throw new \InvalidArgumentException('Insecure URL detected');
}

Applications that manually serialize or forward requests should also ensure the final HTTP client, transport, or serializer rejects invalid URI and header data before writing requests to the network.

References

• https://www.rfc-editor.org/rfc/rfc9112.html#section-3.2
• https://www.rfc-editor.org/rfc/rfc9112.html#section-5
• https://www.rfc-editor.org/rfc/rfc9112.html#section-11.2
• https://www.rfc-editor.org/rfc/rfc9110.html#section-7.2

Impact

guzzlehttp/psr7 did not reject URI host components containing authority delimiters (/, ?, #, @, or \), an embedded port such as host:8080, or IPv6 brackets that do not frame the host (such as [::1 or ::1]). Uri::assertValidHost() rejected only control characters, so these malformed hosts were accepted both when parsing a URI string — including through new Uri(), an absolute-form request target passed to Message::parseRequest(), and the synthetic SERVER_NAME or SERVER_ADDR fallback used by ServerRequest::fromGlobals() — and when setting a host with Uri::withHost(). Because the stored host was not validated, Uri::getHost() could return a value that does not agree with the URI's authority or with the host that is actually used on the wire. For example, Uri::withHost('good.com@evil.com') is accepted, and new Uri('http://[gggg::1]/') produces a getHost() of '[gggg:' while getAuthority() returns '[gggg::1'.

You are affected if your application builds a Uri or calls Uri::withHost() with host data that is wholly or partly attacker-controlled and then relies on Uri::getHost() for a security or routing decision, such as host allowlisting or denylisting, an SSRF guard, cookie scoping, or proxy-bypass selection. You are also affected if you parse, forward, proxy, or re-serialize URIs that come from untrusted raw HTTP messages or from synthetic $_SERVER values. Because getHost() can then disagree with the real connection target, the concrete impact depends on how your application and any downstream HTTP/1.x component use the URI, and may include host-based access-control bypass, server-side request forgery, routing to an unintended host, or Host header confusion. You are not affected if every host you place into a Uri is already trusted and well formed.

Applications using guzzlehttp/guzzle are affected in the same way through Guzzle's use of PSR-7. Guzzle derives the request Host header from the request URI, and its cookie matching and no_proxy proxy-bypass matching both read Uri::getHost(). An application that builds a Guzzle request URI from attacker-controlled host input can therefore have its Host header, cookie scope, or proxy-bypass decision computed against a host that differs from the one Guzzle connects to. This is not the normal request-sending path, and an application that passes only trusted, well-formed URIs to Guzzle and never builds a request URI from attacker-controlled host input is not affected through Guzzle's standard client APIs.

Patches

The issue is patched in 2.12.3 and later. Starting in that release, guzzlehttp/psr7 rejects URI host components that contain authority delimiters, an embedded port, or IPv6 brackets that do not frame the host, both when parsing a URI and via Uri::withHost(), so Uri::getHost() agrees with the URI authority. A framed bracketed literal whose contents are not a valid IPv6 address is preserved rather than rejected, so getHost() still agrees with the authority.

Workarounds

If you cannot upgrade immediately, validate and normalize host values before you build or modify a Uri from untrusted input, and do not treat Uri::getHost() as a trust boundary for a host you have not independently checked. Before passing a host to Uri, reject any value that contains /, ?, #, @, or \, that contains a colon outside a bracketed IPv6 literal, or that has unbalanced brackets. Applications that parse, forward, replay, or re-serialize raw HTTP messages, or that run with attacker-controlled $_SERVER values, should validate the host before calling Message::parseRequest() or ServerRequest::fromGlobals(), and should avoid reparsing untrusted input.

References

• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.2
• https://datatracker.ietf.org/doc/html/rfc3986#section-3.2.3
• https://datatracker.ietf.org/doc/html/rfc6265#section-5.1.3

Impact

guzzlehttp/psr7 did not reject CR/LF characters in certain first-party HTTP start-line fields: the request method, protocol version, and response reason phrase. If an application placed attacker-controlled data into one of those fields and later serialized the PSR-7 message as raw HTTP/1.x, for example with Message::toString() or an equivalent serializer, the serialized message could contain attacker-controlled header lines. The issue can also be reached through Message::parseRequest() or Message::parseResponse() when malformed raw messages are parsed into first-party PSR-7 objects and then serialized again.

Creating or modifying a Request, Response, or other PSR-7 object alone is not sufficient. The issue requires the malformed message to be serialized and written to the network, forwarded, replayed, or otherwise processed by software that does not independently reject the malformed start line. This is not the normal request-sending path used by guzzlehttp/guzzle; applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected.

Applications are most likely to be affected when they manually serialize PSR-7 messages, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, testing, or similar code. Depending on how downstream HTTP/1.1 components parse the serialized message, this may lead to header injection, response splitting, request smuggling, or cache poisoning.

Patches

The issue is patched in 2.12.1 and later. Starting in that release, guzzlehttp/psr7 rejects CR/LF characters in HTTP method, protocol version, and response reason phrase values before storing them in first-party message objects.

Workarounds

If you cannot upgrade immediately, reject CR/LF in untrusted method, protocol version, and reason phrase values before constructing or modifying PSR-7 messages.

Applications that parse, forward, replay, or serialize raw HTTP messages cannot work around the parser entry points by validating only after parsing. They should validate the raw start line before calling Message::parseRequest() or Message::parseResponse(), avoid reparsing untrusted raw messages, or upgrade. If an application runs with attacker-controlled synthetic $_SERVER values, validate REQUEST_METHOD and SERVER_PROTOCOL before calling ServerRequest::fromGlobals().