guzzlehttp/guzzle versions before 7.15.1 contain a denial of service vulnerability in the CookieJar that accepts unlimited Set-Cookie header fields with no size restrictions. Attackers can return many large cookies from a malicious server, causing Guzzle to store excessive data in memory and generate oversized Cookie headers that fail in handlers or destination servers.

Affected: Packagist: guzzlehttp/guzzle

### Impact

In affected versions, Guzzle's built-in `CookieJar` accepts any number of `Set-Cookie` header fields from one response, with no limit on the size of each field. When a later request matches the stored cookies, Guzzle places every match into one generated `Cookie` header without limiting the number of cookies or the total header length.

A malicious or compromised server can therefore return many large cookies, causing Guzzle to store attacker-controlled data in memory and copy it into later request headers. This can increase memory use and processing time. It can also make later requests fail when the generated header exceeds a limit in a handler, HTTP implementation, proxy, or destination server. A server on one sibling host, such as `attacker.example.com`, can also set parent-domain cookies that are later selected for another sibling, such as `service.example.com`. The denial can therefore affect a different service that uses the same jar.

An application is affected when it enables the built-in cookie support, receives an attacker-controlled response, and retains or reuses the jar. The issue affects both built-in handlers because Guzzle manages these cookies itself instead of using libcurl's native cookie engine. cURL addressed a similar denial-of-service issue in CVE-2022-32205 by limiting the cookies it accepts and sends, but those native limits do not protect Guzzle's separate jar. Applications that do not use cookies, use separate jars for untrusted origin…

Affected: Ubuntu:24.04:LTS: guzzle, Ubuntu:26.04:LTS: guzzle

guzzlehttp/guzzle versions before 7.15.1 contain a denial of service vulnerability in the CookieJar that accepts unlimited Set-Cookie header fields with no size restrictions. Attackers can return many large cookies from a malicious server, causing Guzzle to store excessive data in memory and generate oversized Cookie headers that fail in handlers or destination servers.