guzzlehttp/psr7 is a PSR-7 HTTP message library. Versions prior to 1.8.4 and 2.1.1 are vulnerable to improper header parsing. An attacker could sneak in a new line character and pass untrusted values. The issue is patched in 1.8.4 and 2.1.1. There are currently no known workarounds.
https://www.drupal.org/sa-core-2022-006
https://github.com/guzzle/psr7/security/advisories/GHSA-q7rv-6hp3-vh96
https://github.com/guzzle/psr7/pull/486/commits/9a96d9db668b485361ed9de7b5bf1e54895df1dc
https://github.com/guzzle/psr7/pull/485/commits/e55afaa3fc138c89adf3b55a8ba20dc60d17f1f1