Vercel ms Inefficient Regular Expression Complexity vulnerability

Exploitation

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

CVSS

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

EPSS

• CVE-2017-20162: 1.02% estimated exploitation activity in the next 30 days; percentile 63.38 (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, which was classified as problematic, has been found in vercel ms up to 1.x. This issue affects the function parse of the file index.js. The manipulation of the argument str leads to inefficient regular expression complexity. The attack may be initiated remotely. The exploit has been disclosed to the public and may be used. Upgrading to version 2.0.0 is able to address this issue. The name of the patch is caae2988ba2a37765d055c4eee63d383320ee662. It is recommended to upgrade the affected component. The associated identifier of this vulnerability is VDB-217451.

Published by the source

5 Jan 2023, 12:30 UTC

Last modified by the source

4 Nov 2025, 16:42 UTC

Source last checked

26 Oct 2026, 12:38 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-w9mr-4mfr-499f

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-w9mr-4mfr-499f

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# Patch Next advisory brief: CVE-2017-20162

Advisory: Vercel ms Inefficient Regular Expression Complexity vulnerability
IDs: CVE-2017-20162, GHSA-w9mr-4mfr-499f
Record: https://patchnext.com/advisories/cve-2017-20162 (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 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: ms 2.0.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm ms: affected < 2.0.0; fixed in 2.0.0

## Suggested inspection (read-only)
- `npm ls ms --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 ms.
- 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-w9mr-4mfr-499f (OSV record GHSA-w9mr-4mfr-499f lists affected ranges: npm ms >=0 <2.0.0 (fixed))
- Verified: https://github.com/advisories/GHSA-w9mr-4mfr-499f (GitHub-reviewed advisory GHSA-w9mr-4mfr-499f lists affected ranges: npm ms >=0 <2.0.0)

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