GHSA-hwj9-h5mp-3pm3 is a medium-severity (CVSS 5.3) vulnerability in postcss. 2 public exploit references exist, so weaponization risk is real. O3 Security confirms whether GHSA-hwj9-h5mp-3pm3 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Regular Expression Denial of Service in postcss
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-hwj9-h5mp-3pm3 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 372,613 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
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
postcssnpmDescription
The npm package postcss from 7.0.0 and before versions 7.0.36 and 8.2.10 is vulnerable to Regular Expression Denial of Service (ReDoS) during source map parsing.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | postcss | ≥ 7.0.0&&< 7.0.36 | 7.0.36 |
| 📦npm | postcss | ≥ 8.0.0&&< 8.2.10 | 8.2.10 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for postcss. 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 postcss to 7.0.36 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-hwj9-h5mp-3pm3 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-hwj9-h5mp-3pm3 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-hwj9-h5mp-3pm3. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
In Red Hat OpenShift Container Platform (RHOCP), OpenShift ServiceMesh (OSSM) and Red Hat Advanced Cluster Management for Kubernetes (RHACM) the affected containers are behind OpenShift OAuth authentication. This restricts access to the vulnerable nodejs-postcss library to authenticated users only, therefore the…
Frequently Asked Questions
Is GHSA-hwj9-h5mp-3pm3 in your dependencies?
O3 detects GHSA-hwj9-h5mp-3pm3 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.