jsondiffpatch patch APIs are vulnerable to prototype pollution

Exploitation

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

CVSS 4.0

7.8 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N/E:P · score source

EPSS

• CVE-2026-8657: 0.38% estimated exploitation activity in the next 30 days; percentile 31.87 (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.

Versions of the package jsondiffpatch before 0.7.6 are vulnerable to Prototype Pollution via the jsondiffpatch.patch() and jsondiffpatch/formatters/jsonpatch.patch() APIs. An attacker can perform prototype pollution by supplying crafted delta or JSON Patch documents, as attacker-controlled property names and path segments are used to traverse and modify objects without restricting access to special properties like proto or constructor.prototype, allowing modification of Object.prototype.

Published by the source

16 May 2026, 06:30 UTC

Last modified by the source

10 Sep 2026, 03:51 UTC

Source last checked

26 Oct 2026, 13:01 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-j4fx-xxwh-2485

2. Revision 2 · amended · 24 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-j4fx-xxwh-2485

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# Patch Next advisory brief: CVE-2026-8657

Advisory: jsondiffpatch patch APIs are vulnerable to prototype pollution
IDs: CVE-2026-8657, GHSA-j4fx-xxwh-2485
Record: https://patchnext.com/advisories/cve-2026-8657 (revision 3, source checked 26 Oct 2026, 13:01 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: jsondiffpatch 0.7.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm jsondiffpatch: affected < 0.7.6; fixed in 0.7.6

## Suggested inspection (read-only)
- `npm ls jsondiffpatch --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 jsondiffpatch.
- 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-j4fx-xxwh-2485 (OSV record GHSA-j4fx-xxwh-2485 lists affected ranges: npm jsondiffpatch >=0 <0.7.6 (fixed))
- Verified: https://github.com/advisories/GHSA-j4fx-xxwh-2485 (GitHub-reviewed advisory GHSA-j4fx-xxwh-2485 lists affected ranges: npm jsondiffpatch >=0 <0.7.6)

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