CVE-2026-55766 guzzlehttp/psr7: CRLF Injection in HTTP Start-Line Serialization

guzzlehttp/psr7 is a PSR-7 HTTP message library implementation in PHP. Prior to 2.12.1, 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 dat...

CVE-2026-55766

Summary (CVE-2026-55766): guzzlehttp/psr7 (PHP) before 2.12.1 is vulnerable to CRLF injection in the HTTP start-line fields (method, protocol version, reason phrase) when attacker-controlled data ends up in those fields and the message is serialized or forwarded. The flaw requires the malformed m...

guzzlehttp/psr7: CRLF Injection in HTTP Start-Line Serialization

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...

CRLF injection in HTTP start-line serialization

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...