chore(deps): update dependency shell-quote to v1.9.0 [security]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
shell-quote	1.8.4 → 1.9.0

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

CVE-2026-13311 / GHSA-395f-4hp3-45gv

More information

Details

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:

}).reduce(function (prev, arg) { // finalize parsed arguments
    // TODO: replace this whole reduce with a concat
    return typeof arg === 'undefined' ? prev : prev.concat(arg);
}, []);

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: replace this whole reduce with a concat
already flags the construct.

Proof of Concept

const { parse } = require('shell-quote');
const ms = fn => { const t = process.hrtime.bigint(); fn(); return Number(process.hrtime.bigint()-t)/1e6; };
for (const N of [16000, 32000, 64000, 128000]) {
  console.log(N, 'tokens ->', ms(() => parse('x '.repeat(N))).toFixed(0), 'ms');
}

Measured on shell-quote@1.8.4, Node v24:

input (N tokens)	bytes	parse()	ratio vs prev (2× input)
16 000	32 KB	678 ms	—
32 000	64 KB	4 169 ms	×6.2
64 000	128 KB	14 914 ms	×3.6
128 000	256 KB	57 319 ms	×3.8

Time grows ~×4 per 2× input → confirmed O(n²). A ~128 KB input blocks the event loop ~15 s;
~256 KB → ~57 s; a few hundred KB more → minutes.

poc.js

Impact

parse() is synchronous on the main thread; while it copies arrays quadratically the entire
event loop is blocked and the process serves no other requests. Any service that calls parse()
on attacker-influenced input (command parsers, chat-ops / bot command handlers, REPLs,
build-script / arg-string splitters) can be driven to a sustained DoS with a single small
request. No code execution and no data disclosure — availability only.

End-to-end confirmation: a minimal HTTP server that calls parse() on the request body, hit
with one POST of 'x '.repeat(32000) (~63 KB), froze for ~4.5 s. An out-of-process probe
client issuing harmless GET /ping requests (normally ~1 ms) observed 27 consecutive pings
stalled by up to 4374 ms during that single request — i.e. every concurrent client was denied
service for the whole parse. Scaling the body to a few hundred KB extends the outage to minutes.

This is the same class as several accepted 2026 advisories for quadratic-parser DoS on
untrusted input (e.g. markdown-it CVE-2026-48988, js-yaml CVE-2026-53550,
python-multipart CVE-2026-53539). It is distinct from the known shell-quote
command-injection issues (CVE-2021-42740, CVE-2016-10541, CVE-2026-9277), which are all in
quote(), not parse().

Suggested remediation

Replace the O(n²) concat-in-reduce with a linear flatten that pushes into the
accumulator instead of reallocating and copying it on every iteration. Apply the
same shape to the wrapper's acc.concat(s) reduce. A defensive input-length cap on
parse() is a cheap additional stop-gap.

Maintainer note (edit): the originally-suggested Array.prototype.flat() is
ES2019 / Node 11+, but shell-quote declares engines: node >= 0.4, so .flat()
would silently drop support for older runtimes. The fix instead flattens one-level
array tokens with forEach/push — and deliberately not push.apply(...), since
spreading a large array into function arguments can exceed the engine's argument
count limit. Output is byte-identical to the current code across strings, undefined
holes, one-level array tokens, and {op}/{comment}/{op:'glob'} objects, and
finalizing is now linear (1,024,000 tokens in ~150 ms vs ~57 s for 128,000 before).
Thanks for the clear report and PoC — the analysis and reproduction were spot on.

Disclosure

Found by source audit + wall-clock confirmation against 1.8.4 (and verified the same code is
present on main). Reported privately here; no public disclosure until a fix is available.

Severity

• CVSS Score: 8.7 / 10 (High)
• Vector String: 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

References

• https://github.com/ljharb/shell-quote/security/advisories/GHSA-395f-4hp3-45gv
• https://nvd.nist.gov/vuln/detail/CVE-2026-13311
• https://github.com/ljharb/shell-quote/commit/7ff5488599d01c323514f02f5efb74088dd134ec
• https://github.com/ljharb/shell-quote/releases/tag/v1.9.0
• https://www.npmjs.com/package/shell-quote
• https://github.com/advisories/GHSA-395f-4hp3-45gv

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

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Release Notes

ljharb/shell-quote (shell-quote)

v1.9.0

Compare Source

Commits

• [New] add types dca6e21
• [Dev Deps] update eslint 9aa9e8f
• [Fix] parse: finalize tokens in linear time (GHSA-395f-4hp3-45gv) 7ff5488
• [actions] update workflows 75e8497
• [actions] Windows + node 4/6/7: pin eslint to 9 before install, since npm 2/3 cannot stage eslint 10@types/esrecurse 3fb739d
• [actions] retry npm install on Windows to survive npm 2/3 staging-rename flake abe0163
• [actions] Windows + node 5/7: install deps with a modern node b4bafa2
• [Fix] quote: escape leading ~ to prevent shell tilde-expansion 7a76c1a
• [Dev Deps] update auto-changelog, tape 7184b44
• [Dev Deps] apparently jackspeak is no longer in the graph 9ba368a

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[coveralls]

Coverage Report for CI Build 30174713655

Coverage remained the same at 96.842%

Details

• Coverage remained the same as the base build.
• Patch coverage: No coverable lines changed in this PR.
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	764
Covered Lines:	746
Line Coverage:	97.64%
Relevant Branches:	471
Covered Branches:	450
Branch Coverage:	95.54%
Branches in Coverage %:	Yes
Coverage Strength:	2928181.34 hits per line

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💛 - Coveralls