counterpart vulnerable to prototype pollution

Exploitation

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

CVSS

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

EPSS

• CVE-2025-57354: 0.48% estimated exploitation activity in the next 30 days; percentile 41.82 (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 exists in the counterpart library for Node.js and the browser due to insufficient sanitization of user-controlled input in translation key processing. The affected versions prior to 0.18.6 allow attackers to manipulate the library's translation functionality by supplying maliciously crafted keys containing prototype chain elements (e.g., proto ), leading to prototype pollution. This weakness enables adversaries to inject arbitrary properties into the JavaScript Object prototype through the first parameter of the translate method when combined with specific separator configurations, potentially resulting in denial-of-service conditions or remote code execution in vulnerable applications. The issue arises from the library's failure to properly validate or neutralize special characters in translation key inputs before processing.

Published by the source

24 Sep 2025, 18:30 UTC

Last modified by the source

26 Sep 2025, 17:27 UTC

Source last checked

26 Oct 2026, 12:38 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-2488-w585-72ch

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-2488-w585-72ch

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# Patch Next advisory brief: CVE-2025-57354

Advisory: counterpart vulnerable to prototype pollution
IDs: CVE-2025-57354, GHSA-2488-w585-72ch
Record: https://patchnext.com/advisories/cve-2025-57354 (revision 2, source checked 26 Oct 2026, 12:38 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm counterpart: affected <= 0.18.6

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

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on counterpart.
- 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-2488-w585-72ch (OSV record GHSA-2488-w585-72ch lists affected ranges: npm counterpart >=0 <=0.18.6)
- Verified: https://github.com/advisories/GHSA-2488-w585-72ch (GitHub-reviewed advisory GHSA-2488-w585-72ch lists affected ranges: npm counterpart >=0 <=0.18.6)

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