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High, CVSS 8.1amended

Code Injection in pac-resolver

CVE-2021-23406GHSA-9j49-mfvp-vmhm

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (pac-resolver 5.0.0; degenerator 3.0.1), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
8.1 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
  • CVE-2021-23406: 2.94% estimated exploitation activity in the next 30 days; percentile 87.16 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

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.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-9j49-mfvp-vmhm

  2. Revision 1 · created ·

    Published from osv record GHSA-9j49-mfvp-vmhm

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2021-23406

Advisory: Code Injection in pac-resolver
IDs: CVE-2021-23406, GHSA-9j49-mfvp-vmhm
Record: https://patchnext.com/advisories/cve-2021-23406 (revision 2, source checked 26 Oct 2026, 12:21 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: pac-resolver 5.0.0; degenerator 3.0.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm pac-resolver: affected < 5.0.0; fixed in 5.0.0
- npm degenerator: affected < 3.0.1; fixed in 3.0.1

## Suggested inspection (read-only)
- `npm ls pac-resolver --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls degenerator --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on pac-resolver, degenerator.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-9j49-mfvp-vmhm (OSV record GHSA-9j49-mfvp-vmhm lists affected ranges: npm pac-resolver >=0 =0 <3.0.1 (fixed))
- Verified: https://github.com/advisories/GHSA-9j49-mfvp-vmhm (GitHub-reviewed advisory GHSA-9j49-mfvp-vmhm lists affected ranges: npm pac-resolver >=0 =0 <3.0.1)

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