How severe is GHSA-9j49-mfvp-vmhm?

GHSA-9j49-mfvp-vmhm has a CVSS score of 8.1/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by GHSA-9j49-mfvp-vmhm?

GHSA-9j49-mfvp-vmhm affects the following packages: pac-resolver (npm), degenerator (npm). Ecosystems affected: npm.

How do I fix GHSA-9j49-mfvp-vmhm?

Update pac-resolver to 5.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9j49-mfvp-vmhm is resolved across your whole dependency graph.

How do I detect GHSA-9j49-mfvp-vmhm in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pac-resolver. 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.

How do I mitigate GHSA-9j49-mfvp-vmhm if there is no patch (or I can't update yet)?

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 does O3 Security protect against GHSA-9j49-mfvp-vmhm?

O3 pinpoints whether GHSA-9j49-mfvp-vmhm is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-9j49-mfvp-vmhm actively exploited in the wild?

Yes. There are 2 known exploit references for GHSA-9j49-mfvp-vmhm, including 2 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for GHSA-9j49-mfvp-vmhm?

GHSA-9j49-mfvp-vmhm has an EPSS (Exploit Prediction Scoring System) score of 2.9%, placing it in the 85th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

When was GHSA-9j49-mfvp-vmhm published, and has it been updated?

GHSA-9j49-mfvp-vmhm was published on September 2, 2021 and was last updated on January 14, 2025. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

GHSA-9j49-mfvp-vmhm

HIGH

Code Injection in pac-resolver

Also known asCVE-2021-23406

Published

Sep 2, 2021

Updated

Jan 14, 2025

Affected

2 pkgs

Patched

2 / 2

Exploits

2 known

EPSS Exploitation Probability

via FIRST.org ↗

2.9%probability of exploitation in next 30 days

Lower Risk85th percentile+1.86%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

2 pkgs affected

📦pac-resolver📦degenerator

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm packages — download data is not available via public APIs for these ecosystems.

Description

This affects the package pac-resolver before 5.0.0. This can occur when used with untrusted input, due to unsafe PAC file handling. NOTE: The fix for this vulnerability is applied in the node-degenerator library, a dependency written by the same maintainer.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`pac-resolver`	all versions	5.0.0
📦npm	`degenerator`	all versions	3.0.1

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

This affects the package pac-resolver before 5.0.0. This can occur when …

snyk.ioNVDAug 2021

This affects the package pac-resolver before 5.0.0. This can occur when …

snyk.ioNVDAug 2021

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pac-resolver. 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 pac-resolver to 5.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-9j49-mfvp-vmhm 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-9j49-mfvp-vmhm 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-9j49-mfvp-vmhm. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

This affects the package pac-resolver before 5.0.0. This can occur when used with untrusted input, due to unsafe PAC file handling. **NOTE:** The fix for this vulnerability is applied in the node-degenerator library, a dependency written by the same maintainer.

O3 Security · Impact-Aware SCA

Is GHSA-9j49-mfvp-vmhm in your dependencies?

O3 detects GHSA-9j49-mfvp-vmhm across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works