cvedb.io
CVE-2026-55766
MEDIUM · CVSS 4.8
EPSS exploitation probability: 0%
Published 2026-06-23T16:17:03.127 · Last modified 2026-06-30T17:17:36.993

Summary

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 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 is

Affected products

guzzlephp — psr-7

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References

This product uses data from the NVD API but is not endorsed or certified by the NVD. Informational only; not professional security advice.