CVE-2021-23368 is a medium-severity (CVSS 5.3) vulnerability in postcss. 2 public exploit references exist, so weaponization risk is real. A fix is available for postcss — see the affected versions and patch details below.
Regular Expression Denial of Service in postcss
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-23368 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 398,142 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
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 | 7.0.36npm install postcss@7.0.36 |
| 📦npm | postcss | ≥ 8.0.0&&< 8.2.10 | 8.2.10npm install postcss@8.2.10 |
Affected Products
postcsspostcssResearch 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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update postcss to 7.0.36 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-23368 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
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…
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat OpenShift Container Platform 4.8 | openshift4/ose-console:v4.8.0-202107010336.p0.git.188a490.assembly.stream | RHSA-2021:2438 |
| Red Hat Quay 3 | quay/quay-rhel8:v3.6.0-62 | RHSA-2021:3917 |
Frequently Asked Questions
Is CVE-2021-23368 in your dependencies?
Find it across npm, including transitive dependencies.