CVE-2022-21222 is a medium-severity (CVSS 5.3) CWE-1333 vulnerability in css-what. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for css-what — see the affected versions and patch details below.
Regular Expression Denial of Service (ReDoS)
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2022-21222.
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.
css-whatnpmDescription
The package css-what before 2.1.3 are vulnerable to Regular Expression Denial of Service (ReDoS) due to the usage of insecure regular expression in the re_attr variable of index.js. The exploitation of this vulnerability could be triggered via the parse function.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | css-what | all versions | 2.1.3npm install css-what@2.1.3 |
Affected Products
css-whatcss-what_projectResearch 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 css-what, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update css-what to 2.1.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2022-21222 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.
Frequently Asked Questions
Is CVE-2022-21222 in your dependencies?
Find it across npm, including transitive dependencies.