shell-quote: Quadratic-complexity Denial of Service in parse() (CWE-407)

Exploitation

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

CVSS 4.0

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

EPSS

• CVE-2026-13311: 0.36% estimated exploitation activity in the next 30 days; percentile 29.87 (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.

Summary shell-quote's parse() finalizes its token list with a reduce that uses Array.prototype.concat as the accumulator. Each prev.concat(arg) copies the entire growing array, so parse() runs in O(n²) in the number of tokens. An unauthenticated attacker who can submit a string to any code path that calls parse() on it can block the single-threaded Node.js event loop for tens of seconds with a small input — a denial of service. The trigger needs no shell metacharacters (plain space-separated words suffice), so input filters that only screen for ;, |, $, or backticks do not help. Root cause parse.js (lines 200–203), in parseInternal — this path runs on every parse() call: prev.concat(arg) allocates a new array and copies all of prev on every iteration, so producing an N-token result costs 1 + 2 + … + N = O(N²) copies. A second acc.concat(s) reduce in the module.exports wrapper (lines 211–224, reached only when env is a function) has the same shape. The maintainer's own // TODO:…

Published by the source

20 Jul 2026, 21:49 UTC

Last modified by the source

10 Sep 2026, 03:51 UTC

Source last checked

26 Oct 2026, 12:57 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-395f-4hp3-45gv

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-395f-4hp3-45gv

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# Patch Next advisory brief: CVE-2026-13311

Advisory: shell-quote: Quadratic-complexity Denial of Service in `parse()` (CWE-407)
IDs: CVE-2026-13311, GHSA-395f-4hp3-45gv
Record: https://patchnext.com/advisories/cve-2026-13311 (revision 3, source checked 26 Oct 2026, 12:57 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: shell-quote 1.9.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm shell-quote: affected <= 1.8.4; fixed in 1.9.0

## Suggested inspection (read-only)
- `npm ls shell-quote --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 shell-quote.
- 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-395f-4hp3-45gv (OSV record GHSA-395f-4hp3-45gv lists affected ranges: npm shell-quote >=0 <1.9.0 (fixed))
- Verified: https://github.com/advisories/GHSA-395f-4hp3-45gv (GitHub-reviewed advisory GHSA-395f-4hp3-45gv lists affected ranges: npm shell-quote >=0 <=1.8.4)

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