Ruby/puma/5.6.0

Puma HTTP Request/Response Smuggling vulnerability

Impact

Prior to versions 6.4.2 and 5.6.8, puma exhibited dangerous behavior when parsing chunked transfer encoding bodies.

Fixed versions limit the size of chunk extensions. Without this limit, an attacker could cause unbounded resource (CPU, network bandwidth) consumption.

Patches

The vulnerability has been fixed in 6.4.2 and 5.6.8.

Workarounds

No known workarounds.

References

• HTTP Request Smuggling
• Open an issue in Puma
• See our security policy

Puma vulnerable to HTTP Request Smuggling

When using Puma behind a proxy that does not properly validate that the incoming HTTP request matches the RFC7230 standard, Puma and the frontend proxy may disagree on where a request starts and ends. This would allow requests to be smuggled via the front-end proxy to Puma.

The following vulnerabilities are addressed by this advisory: - Lenient parsing of Transfer-Encoding headers, when unsupported encodings should be rejected and the final encoding must be chunked. - Lenient parsing of malformed Content-Length headers and chunk sizes, when only digits and hex digits should be allowed. - Lenient parsing of duplicate Content-Length headers, when they should be rejected. - Lenient parsing of the ending of chunked segments, when they should end with \r\n.

The vulnerability has been fixed in 5.6.4 and 4.3.12. When deploying a proxy in front of Puma, turning on any and all functionality to make sure that the request matches the RFC7230 standard.

These proxy servers are known to have good behavior re: this standard and upgrading Puma may not be necessary. Users are encouraged to validate for themselves.

• Nginx (latest)
• Apache (latest)
• Haproxy 2.5+
• Caddy (latest)
• Traefik (latest)

Puma used with Rails may lead to Information Exposure

Impact

Prior to puma version 5.6.2, puma may not always call close on the response body. Rails, prior to version 7.0.2.2, depended on the response body being closed in order for its CurrentAttributes implementation to work correctly.

From Rails:

Under certain circumstances response bodies will not be closed, for example a bug in a webserver[1] or a bug in a Rack middleware. In the event a response is not notified of a close, ActionDispatch::Executor will not know to reset thread local state for the next request. This can lead to data being leaked to subsequent requests, especially when interacting with ActiveSupport::CurrentAttributes.

The combination of these two behaviors (Puma not closing the body + Rails' Executor implementation) causes information leakage.

Patches

This problem is fixed in Puma versions 5.6.2 and 4.3.11.

This problem is fixed in Rails versions 7.02.2, 6.1.4.6, 6.0.4.6, and 5.2.6.2.

See: https://github.com/advisories/GHSA-wh98-p28r-vrc9 for details about the rails vulnerability

Upgrading to a patched Rails or Puma version fixes the vulnerability.

Workarounds

Upgrade to Rails versions 7.02.2, 6.1.4.6, 6.0.4.6, and 5.2.6.2.

The Rails CVE includes a middleware that can be used instead.

References

• Rails CVE: CVE-2022-23633

For more information

If you have any questions or comments about this advisory: * Open an issue in puma * See our security policy

Information Exposure with Puma when used with Rails

Impact

Prior to puma version 5.6.2, puma may not always call close on the response body. Rails, prior to version 7.0.2.2, depended on the response body being closed in order for its CurrentAttributes implementation to work correctly.

From Rails:

Under certain circumstances response bodies will not be closed, for example a bug in a webserver[1] or a bug in a Rack middleware. In the event a response is not notified of a close, ActionDispatch::Executor will not know to reset thread local state for the next request. This can lead to data being leaked to subsequent requests, especially when interacting with ActiveSupport::CurrentAttributes.

The combination of these two behaviors (Puma not closing the body + Rails' Executor implementation) causes information leakage.

Patches

This problem is fixed in Puma versions 5.6.2 and 4.3.11.

This problem is fixed in Rails versions 7.02.2, 6.1.4.6, 6.0.4.6, and 5.2.6.2.

See: https://github.com/advisories/GHSA-wh98-p28r-vrc9 for details about the rails vulnerability

Upgrading to a patched Rails or Puma version fixes the vulnerability.

Workarounds

Upgrade to Rails versions 7.0.2.2, 6.1.4.6, 6.0.4.6, and 5.2.6.2.

The Rails CVE includes a middleware that can be used instead.

HTTP Request Smuggling in puma

Impact

When using Puma behind a proxy that does not properly validate that the incoming HTTP request matches the RFC7230 standard, Puma and the frontend proxy may disagree on where a request starts and ends. This would allow requests to be smuggled via the front-end proxy to Puma.

The following vulnerabilities are addressed by this advisory: - Lenient parsing of Transfer-Encoding headers, when unsupported encodings should be rejected and the final encoding must be chunked. - Lenient parsing of malformed Content-Length headers and chunk sizes, when only digits and hex digits should be allowed. - Lenient parsing of duplicate Content-Length headers, when they should be rejected. - Lenient parsing of the ending of chunked segments, when they should end with \r\n.

Patches

The vulnerability has been fixed in 5.6.4 and 4.3.12.

Workarounds

When deploying a proxy in front of Puma, turning on any and all functionality to make sure that the request matches the RFC7230 standard.

These proxy servers are known to have good behavior re: this standard and upgrading Puma may not be necessary. Users are encouraged to validate for themselves.

• Nginx (latest)
• Apache (latest)
• Haproxy 2.5+
• Caddy (latest)
• Traefik (latest)

References

HTTP Request Smuggling