Starcounter-Jack JSON-Patch Prototype Pollution vulnerability

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

EPSS

• CVE-2021-4279: 1.16% estimated exploitation activity in the next 30 days; percentile 67.09 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

A vulnerability has been found in Starcounter-Jack JSON-Patch up to 3.1.0 and classified as problematic. This vulnerability affects unknown code. The manipulation leads to improperly controlled modification of object prototype attributes ('prototype pollution'). The attack can be initiated remotely. The exploit has been disclosed to the public and may be used. Upgrading to version 3.1.1 can address this issue. The name of the patch is 7ad6af41eabb2d799f698740a91284d762c955c9. It is recommended to upgrade the affected component. VDB-216778 is the identifier assigned to this vulnerability.

Published by the source

25 Dec 2022, 21:30 UTC

Last modified by the source

1 Mar 2024, 14:21 UTC

Source last checked

26 Oct 2026, 12:30 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-8gh8-hqwg-xf34

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-8gh8-hqwg-xf34

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# Patch Next advisory brief: CVE-2021-4279

Advisory: Starcounter-Jack JSON-Patch Prototype Pollution vulnerability
IDs: CVE-2021-4279, GHSA-8gh8-hqwg-xf34
Record: https://patchnext.com/advisories/cve-2021-4279 (revision 2, source checked 26 Oct 2026, 12:30 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: fast-json-patch 3.1.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm fast-json-patch: affected < 3.1.1; fixed in 3.1.1

## Suggested inspection (read-only)
- `npm ls fast-json-patch --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 fast-json-patch.
- 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-8gh8-hqwg-xf34 (OSV record GHSA-8gh8-hqwg-xf34 lists affected ranges: npm fast-json-patch >=0 <3.1.1 (fixed))
- Verified: https://github.com/advisories/GHSA-8gh8-hqwg-xf34 (GitHub-reviewed advisory GHSA-8gh8-hqwg-xf34 lists affected ranges: npm fast-json-patch >=0 <3.1.1)

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