GHSA-p9pc-299p-vxgp is a medium-severity (CVSS 5.3) vulnerability in yargs-parser. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether GHSA-p9pc-299p-vxgp is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
yargs-parser Vulnerable to Prototype Pollution
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.
yargs-parsernpmDescription
Affected versions of yargs-parser are vulnerable to prototype pollution. Arguments are not properly sanitized, allowing an attacker to modify the prototype of Object, causing the addition or modification of an existing property that will exist on all objects.
Parsing the argument --foo.__proto__.bar baz' adds a bar property with value baz to all objects. This is only exploitable if attackers have control over the arguments being passed to yargs-parser.
Recommendation
Upgrade to versions 13.1.2, 15.0.1, 18.1.1 or later.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | yargs-parser | ≥ 6.0.0&&< 13.1.2 | 13.1.2 |
| 📦npm | yargs-parser | ≥ 14.0.0&&< 15.0.1 | 15.0.1 |
| 📦npm | yargs-parser | ≥ 16.0.0&&< 18.1.1 | 18.1.1 |
| 📦npm | yargs-parser | all versions | 5.0.1 |
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 yargs-parser. 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 yargs-parser to 13.1.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-p9pc-299p-vxgp 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-p9pc-299p-vxgp 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-p9pc-299p-vxgp. 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.
Frequently Asked Questions
Is GHSA-p9pc-299p-vxgp in your dependencies?
O3 detects GHSA-p9pc-299p-vxgp across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.