messageformat has a prototype pollution vulnerability

Exploitation

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

CVSS 4.0

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

EPSS

• CVE-2025-57349: 0.40% estimated exploitation activity in the next 30 days; percentile 34.53 (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.

The messageformat package, an implementation of the Unicode MessageFormat 2 specification for JavaScript, is vulnerable to prototype pollution due to improper handling of message key paths in versions prior to 2.3.0. The flaw arises when processing nested message keys containing special characters (e.g., proto ), which can lead to unintended modification of the JavaScript Object prototype. This vulnerability may allow a remote attacker to inject properties into the global object prototype via specially crafted message input, potentially causing denial of service or other undefined behaviors in applications using the affected component.

Published by the source

24 Sep 2025, 21:30 UTC

Last modified by the source

25 Sep 2025, 17:12 UTC

Source last checked

25 Oct 2026, 00:30 UTC

1. Revision 2 · amended · 25 Oct 2026

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

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-xfqm-j7pc-xrfc

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# Patch Next advisory brief: CVE-2025-57349

Advisory: messageformat has a prototype pollution vulnerability
IDs: CVE-2025-57349, GHSA-xfqm-j7pc-xrfc
Record: https://patchnext.com/advisories/cve-2025-57349 (revision 2, source checked 25 Oct 2026, 00:30 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 1.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: messageformat 3.0.0-beta.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm messageformat: affected < 3.0.0-beta.0; fixed in 3.0.0-beta.0

## Suggested inspection (read-only)
- `npm ls messageformat --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 messageformat.
- 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-xfqm-j7pc-xrfc (OSV record GHSA-xfqm-j7pc-xrfc lists affected ranges: npm messageformat >=0 <3.0.0-beta.0 (fixed))

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