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guzzlehttp/psr7 rejects CR/LF in HTTP method, protocol version, and reason phrase

guzzlehttp/psr7 now rejects CR/LF characters in HTTP method, protocol version, and response reason phrase values before storing them in first-party message obje

20 Jun 2026Read 1 minSeverity: schedule it

What changed

guzzlehttp/psr7 now rejects CR/LF characters in HTTP method, protocol version, and response reason phrase values before storing them in first-party message objects.

Who it affects

Applications that manually serialize PSR-7 messages, forward raw HTTP messages, or use custom transports, proxying, crawling, webhook delivery, testing, or similar code. Applications using guzzlehttp/psr7 only through Guzzle's standard HTTP client APIs are not expected to be affected.

What to do today

Upgrade to version 2.12.1 or later. If unable to upgrade, reject CR/LF in untrusted method, protocol version, and reason phrase values before constructing or modifying PSR-7 messages.

The trail
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