CVE-2021-25952 is a critical-severity (CVSS 9.8) CWE-1321 vulnerability in just-safe-set. 1 public exploit reference exists, so weaponization risk is real. A fix is available for just-safe-set — see the affected versions and patch details below.
Prototype polluation in just-safe-set
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-25952 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,386 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.
just-safe-setnpmDescription
Prototype pollution vulnerability in ‘just-safe-set’ versions 1.0.0 through 2.2.1 allows an attacker to cause a denial of service and may lead to remote code execution.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | just-safe-set | ≥ 1.0.0&&< 2.2.2 | 2.2.2npm install just-safe-set@2.2.2 |
Affected Products
just-safe-setjust-safe-set_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 just-safe-set, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update just-safe-set to 2.2.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-25952 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.
Frequently Asked Questions
Is CVE-2021-25952 in your dependencies?
Find it across npm, including transitive dependencies.