GHSA-cwmx-hcrq-mhc3
HIGHCross-domain cookie leakage in Guzzle
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
guzzlehttp/guzzle🐘guzzlehttp/guzzleReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Impact
Previous version of Guzzle contain a vulnerability with the cookie middleware. The vulnerability is that it is not checked if the cookie domain equals the domain of the server which sets the cookie via the Set-Cookie header, allowing a malicious server to set cookies for unrelated domains. For example an attacker at www.example.com might set a session cookie for api.example.net, logging the Guzzle client into their account and retrieving private API requests from the security log of their account.
Note that our cookie middleware is disabled by default, so most library consumers will not be affected by this issue. Only those who manually add the cookie middleware to the handler stack or construct the client with ['cookies' => true] are affected. Moreover, those who do not use the same Guzzle client to call multiple domains and have disabled redirect forwarding are not affected by this vulnerability.
Patches
Affected Guzzle 7 users should upgrade to Guzzle 7.4.3 as soon as possible. Affected users using any earlier series of Guzzle should upgrade to Guzzle 6.5.6 or 7.4.3.
Workarounds
If you do not need support for cookies, turn off the cookie middleware. It is already off by default, but if you have turned it on and no longer need it, turn it off.
References
For more information
If you have any questions or comments about this advisory, please get in touch with us in #guzzle on the PHP HTTP Slack. Do not report additional security advisories in that public channel, however - please follow our vulnerability reporting process.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | guzzlehttp/guzzle | all versions | 6.5.6 |
| 🐘Packagist | guzzlehttp/guzzle | ≥ 7.0.0&&< 7.4.3 | 7.4.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for guzzlehttp/guzzle. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update guzzlehttp/guzzle to 6.5.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-cwmx-hcrq-mhc3 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-cwmx-hcrq-mhc3 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-cwmx-hcrq-mhc3. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-cwmx-hcrq-mhc3 in your dependencies?
O3 detects GHSA-cwmx-hcrq-mhc3 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.