GHSA-w3w9-vrf5-8mx8 is a medium-severity (CVSS 5.3) Improper Input Validation vulnerability in react/http. A fix is available for react/http — see the affected versions and patch details below.
ReactPHP's HTTP server parses encoded cookie names so malicious `__Host-` and `__Secure-` cookies can be sent
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-w3w9-vrf5-8mx8.
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.
How urgent is this, really
GHSA-w3w9-vrf5-8mx8 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,166 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
react/httpReal-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
In ReactPHP's HTTP server component versions below v1.7.0, when ReactPHP is processing incoming HTTP cookie values, the cookie names are url-decoded. This may lead to cookies with prefixes like __Host- and __Secure- confused with cookies that decode to such prefix, thus leading to an attacker being able to forge cookie which is supposed to be secure. See also CVE-2020-7070 and CVE-2020-8184 for more information.
Patches
- https://github.com/reactphp/http/commit/663c9a3b77b71463fa7fcb76a6676ffd16979dd6 - Fixed in reactphp/http
v1.7.0
Workarounds
Infrastructure or DevOps can place a reverse proxy in front of the ReactPHP HTTP server to filter out any unexpected Cookie request headers.
References
- CVE-2020-7070, https://bugs.php.net/bug.php?id=79699 and https://github.com/php/php-src/commit/6559fe912661ca5ce5f0eeeb591d928451428ed0
- CVE-2020-8184, https://hackerone.com/reports/895727 and https://github.com/rack/rack/commit/1f5763de6a9fe515ff84992b343d63c88104654c
- Originally introduced via https://github.com/reactphp/http/pull/175
Credits
- Thanks to Marco Squarcina (TU Wien) for reporting this and working with us to coordinate this security advisory
For more information
If you have any questions or comments about this advisory:
- Join the discussion
- Email us at [email protected]
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | react/http | ≥ 0.7.0&&< 1.7.0 | 1.7.0composer require react/http:^1.7.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for react/http, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update react/http to 1.7.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-w3w9-vrf5-8mx8 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-w3w9-vrf5-8mx8 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-w3w9-vrf5-8mx8. 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-w3w9-vrf5-8mx8 in your dependencies?
O3 Security finds GHSA-w3w9-vrf5-8mx8 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.