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php · guzzlehttp/guzzleHeads-up

guzzlehttp/guzzle CookieJar Accepts Dot-Only Domain Attribute

CookieJar incorrectly accepts cookies with a dot-only Domain attribute, allowing them to match any request host.

20 Jun 2026Read 1 minSeverity: schedule it

What changed

CookieJar incorrectly accepts cookies with a dot-only Domain attribute, allowing them to match any request host. Fixed in 7.12.1 by rejecting dot-only domains and preventing empty normalized domain from matching.

Who it affects

Applications using Guzzle's cookie support (e.g., new Client(['cookies' => true]) or shared CookieJar) that reuse the same jar across attacker-controlled and trusted origins.

What to do today

Upgrade to guzzlehttp/guzzle version 7.12.1 or later. If unable to upgrade, use separate CookieJar instances per origin or disable cookie handling for untrusted hosts.

The trail
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