chore(deps): update dependency js-yaml@<3.15.0 to v4 [security]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
js-yaml@<3.15.0	^3.15.0 → ^4.3.1

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JS-YAML: Quadratic CPU consumption in !!omap resolution (3.x and 4.x) — CVE-2026-59870 fix not backported

GHSA-5p4m-2wfm-xmqj

More information

Details

Quadratic CPU consumption in !!omap resolution (js-yaml 3.x and 4.x)

Summary

resolveYamlOmap() enforces key uniqueness for !!omap sequences with a linear
scan (objectKeys.indexOf(...)) inside the per-element loop, making resolution
O(n²) in the number of entries. A modestly sized YAML document therefore
consumes disproportionate CPU inside yaml.load(), giving a denial of service
against any consumer that parses untrusted YAML.

!!omap is registered in the default schema
(lib/schema/default.js → require('../type/omap')), so a plain
yaml.load(untrustedInput) with no options is affected — no custom schema or
non-default configuration is required.

This is the same weakness as CVE-2026-59870 / GHSA-724g-mxrg-4qvm, which was
fixed in the 5.x line in 5.2.1. That fix was never backported: both currently
maintained legacy lines still carry the original implementation.

Affected versions

Line	Latest tested	Status
3.x	3.15.0	Affected — objectKeys.indexOf(pairKey) at lib/type/omap.js:29
4.x	4.3.0	Affected — objectKeys.indexOf(pairKey) at lib/type/omap.js:30
5.x	5.2.2	Not affected — fixed in 5.2.1 (uses a Set)

Both figures are the newest release of each line at the time of writing, so
this is not a "you are on an old version" issue.

Details

lib/type/omap.js (js-yaml 4.3.0):

if (objectKeys.indexOf(pairKey) === -1) objectKeys.push(pairKey)
else return false

objectKeys grows by one element per entry, and Array.prototype.indexOf is a
linear scan, so resolving an n-entry !!omap performs roughly
1 + 2 + … + n comparisons — quadratic in n. The work happens synchronously
inside yaml.load(), blocking the event loop for its whole duration.

The 5.x line already solves exactly this by tracking seen keys in a Set
(src/tag/sequence/omap.ts):

if (carrier.seen.has(key)) return 'duplicate key in ordered map'
carrier.seen.add(key)

Proof of concept

// poc.js  —  node poc.js
const yaml = require('js-yaml');
const doc = n => '!!omap\n' + Array.from({length: n}, (_, i) => `- k${i}: ${i}`).join('\n') + '\n';

for (const n of [10000, 20000, 40000, 80000]) {
  const d = doc(n), t = Date.now();
  yaml.load(d);                      // default schema, no options
  console.log(`n=${n} bytes=${d.length} load=${Date.now() - t}ms`);
}

Measured (node v20.20.2, default heap, no flags)

js-yaml 4.3.0

n=10000  bytes=137787   load=54ms
n=20000  bytes=297787   load=169ms
n=40000  bytes=617787   load=646ms
n=80000  bytes=1257787  load=2607ms

js-yaml 3.15.0

n=10000  bytes=137787   load=53ms
n=20000  bytes=297787   load=166ms
n=40000  bytes=617787   load=641ms
n=80000  bytes=1257787  load=2567ms

Runtime grows by a factor of ~4 for each doubling of n, which is the
signature of O(n²) (linear growth would be ~2×).

Scaling further: a 2.48 MB document with 150,000 entries blocked
yaml.load() for 10.8 seconds.

Impact

Any service that parses attacker-influenced YAML with js-yaml 3.x or 4.x can be
stalled with a small input. Because the loop is synchronous, a single request
blocks the Node.js event loop and stalls every other request in the process —
so the amplification is per-process, not just per-request.

Suggested severity: consistent with CVE-2026-59870 (the same weakness in
5.x), i.e. Availability-only impact, network attack vector, no privileges or
user interaction required.

Suggested fix

Mirror the 5.x fix — replace the linear scan with a Set:

// lib/type/omap.js
const seen = new Set()
// ...
if (seen.has(pairKey)) return false
seen.add(pairKey)

This preserves the existing duplicate-key rejection semantics exactly while
making resolution O(n). A maxOmapLength-style cap would also work, but the
Set matches what 5.x already ships and requires no new option.

References

• CVE-2026-59870 / GHSA-724g-mxrg-4qvm — same weakness in 5.0.0–5.2.0, fixed in 5.2.1
• lib/type/omap.js (3.x, 4.x) — the affected resolver
• lib/schema/default.js — registers !!omap in the default schema

Discovery

Found by an automated static-analysis and executed-proof-of-concept scanner run
against js-yaml 4.2.0, then manually verified against 3.15.0 and 4.3.0 by
executing the proof of concept above. All timings in this report were measured
on the current releases of each line, not on the version originally scanned.

Severity

• CVSS Score: 7.5 / 10 (High)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

• https://github.com/nodeca/js-yaml/security/advisories/GHSA-5p4m-2wfm-xmqj
• https://github.com/advisories/GHSA-5p4m-2wfm-xmqj

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

---

Release Notes

nodeca/js-yaml (js-yaml@<3.15.0)

v4.3.1

Compare Source

v4.3.0

Compare Source

v4.2.0

Compare Source

Added

• Added docs/safety.md with notes about processing untrusted YAML.
• Added maxDepth (100) loader option. Not a problem, but gives a better
  exception instead of RangeError on stack overflow.
• Added maxMergeSeqLength (20) loader option. Not a problem after merge fix,
  but an additional restriction for safety.
• Added sourcemaps to dist/ builds.

Changed

• Stop resolving numbers with underscores as numeric scalars, #​627.
• Switched dev toolchains to Vite / neostandard.
• Updated demo.
• Reorganized tests.
• dist/ files are no longer kept in the repository.

Fixed

• Fix parsing of properties on the first implicit block mapping key, #​62.
• Fix trailing whitespace handling when folding flow scalar lines, #​307.
• Reject top-level block scalars without content indentation, #​280.
• Ensure numbers survive round-trip, #​737.
• Fix test coverage for issue #​221.
• Fix flow scalar trailing whitespace folding, #​307.
• Fix digits in YAML named tag handles.

Security

• Fix potential DoS via quadratic complexity in merge - deduplicate repeated
  elements (makes sense for malformed files > 10K).

v4.1.1

Compare Source

Security

• Fix prototype pollution issue in yaml merge (<<) operator.

v4.1.0

Compare Source

Added

• Types are now exported as yaml.types.XXX.
• Every type now has options property with original arguments kept as they were
  (see yaml.types.int.options as an example).

Changed

• Schema.extend() now keeps old type order in case of conflicts
  (e.g. Schema.extend([ a, b, c ]).extend([ b, a, d ]) is now ordered as abcd instead of cbad).

v4.0.0

Compare Source

Changed

• Check migration guide in docs for details of all breaking changes.
• Breaking: "unsafe" tags !!js/function, !!js/regexp, !!js/undefined are
  moved to js-yaml-js-types package.
• Breaking: removed safe* functions. Use load, loadAll, dump
  instead which are all now safe by default.
• yaml.DEFAULT_SAFE_SCHEMA and yaml.DEFAULT_FULL_SCHEMA are removed, use
  yaml.DEFAULT_SCHEMA instead.
• yaml.Schema.create(schema, tags) is removed, use schema.extend(tags) instead.
• !!binary now always mapped to Uint8Array on load.
• Reduced nesting of /lib folder.
• Parse numbers according to YAML 1.2 instead of YAML 1.1 (01234 is now decimal,
  0o1234 is octal, 1:23 is parsed as string instead of base60).
• dump() no longer quotes :, [, ], (, ) except when necessary, #​470, #​557.
• Line and column in exceptions are now formatted as (X:Y) instead of
  at line X, column Y (also present in compact format), #​332.
• Code snippet created in exceptions now contains multiple lines with line numbers.
• dump() now serializes undefined as null in collections and removes keys with
  undefined in mappings, #​571.
• dump() with skipInvalid=true now serializes invalid items in collections as null.
• Custom tags starting with ! are now dumped as !tag instead of !<!tag>, #​576.
• Custom tags starting with tag:yaml.org,2002: are now shorthanded using !!, #​258.

Added

• Added .mjs (es modules) support.
• Added quotingType and forceQuotes options for dumper to configure
  string literal style, #​290, #​529.
• Added styles: { '!!null': 'empty' } option for dumper
  (serializes { foo: null } as "foo: "), #​570.
• Added replacer option (similar to option in JSON.stringify), #​339.
• Custom Tag can now handle all tags or multiple tags with the same prefix, #​385.

Fixed

• Astral characters are no longer encoded by dump(), #​587.
• "duplicate mapping key" exception now points at the correct column, #​452.
• Extra commas in flow collections (e.g. [foo,,bar]) now throw an exception
  instead of producing null, #​321.
• __proto__ key no longer overrides object prototype, #​164.
• Removed bower.json.
• Tags are now url-decoded in load() and url-encoded in dump()
  (previously usage of custom non-ascii tags may have led to invalid YAML that can't be parsed).
• Anchors now work correctly with empty nodes, #​301.
• Fix incorrect parsing of invalid block mapping syntax, #​418.
• Throw an error if block sequence/mapping indent contains a tab, #​80.

v3.15.1

Compare Source

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[devin-ai-integration]

Devin Review found 2 potential issues.

View 1 additional finding in Devin Review.

[devin-ai-integration]

🟡 Vulnerable YAML parser version remains in use for most dependencies after the security update

The rule covering the current 4.x line still pins to the version the advisory calls vulnerable ('js-yaml@>=4.0.0 <4.3.0': ^4.3.0 in pnpm-workspace.yaml:43), so most dependencies keep resolving that vulnerable version and the intended security fix is not actually applied.
Impact: The denial-of-service issue the update is meant to fix stays present in the installed dependency tree.

Lockfile still resolves js-yaml 4.3.0 for eslint and changesets

pnpm-lock.yaml:4318 and pnpm-lock.yaml:8457 still contain js-yaml@4.3.0, and it is the resolved version for @changesets/parse (pnpm-lock.yaml:5768), @eslint/eslintrc (pnpm-lock.yaml:5978) and eslint (pnpm-lock.yaml:7893). Per the advisory in this PR, 4.3.0 is affected and 4.3.1 carries the fix, so the 4.x override should target ^4.3.1 (which is already whitelisted in minimumReleaseAgeExclude).

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[devin-ai-integration]

Devin Review found 2 new potential issues.

View 1 additional finding in Devin Review.

[devin-ai-integration]

🔴 Release/versioning tooling crashes because an old YAML reader is forced onto an incompatible major version

The dependency rule for old YAML parsers is redirected to a new major version ('js-yaml@<3.15.0': ^4.3.1 in pnpm-workspace.yaml:41) even though a package still bundled in the lockfile only works with the old one, so the changesets release tooling throws as soon as it reads the workspace file.
Impact: Running changeset commands (e.g. version/publish in CI) fails outright, blocking releases.

Transitive dependency read-yaml-file@1.1.0 calls the removed yaml.safeLoad API

pnpm-lock.yaml:9014-9019 shows read-yaml-file@1.1.0 now resolving js-yaml: 4.3.1 (previously 3.x, matched by the <3.15.0 override range). read-yaml-file@1.1.0 declares js-yaml: ^3.6.1 and its implementation calls yaml.safeLoad(...). js-yaml 4 removed safeLoad, replacing it with a stub that throws Function yaml.safeLoad is removed in js-yaml 4. read-yaml-file is a dependency of @manypkg/get-packages@1.1.3 (pnpm-lock.yaml:6340-6347), which every @changesets/* package in this repo depends on (pnpm-lock.yaml:5663-5790) and which uses it to parse pnpm-workspace.yaml when enumerating workspace packages.

A safer scoping would keep the 3.x range on the 3.x line (e.g. 'js-yaml@<3.15.0': ^3.15.0) and rely on the separate 4.x override for 4.x consumers, or bump read-yaml-file to a version compatible with js-yaml 4.

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[devin-ai-integration]

Devin Review found 1 new potential issue.

View 1 additional finding in Devin Review.

[devin-ai-integration]

🟨 Vulnerable js-yaml 4.3.0 still resolved despite security override

The override for the 4.x line still targets ^4.3.0 (pnpm-workspace.yaml:43), and the lockfile keeps resolving js-yaml@4.3.0 for eslint and changesets (pnpm-lock.yaml:4318, pnpm-lock.yaml:5768, pnpm-lock.yaml:5978, pnpm-lock.yaml:7893). Per the advisory this PR cites (GHSA-5p4m-2wfm-xmqj), 4.3.0 is affected by quadratic CPU consumption in !!omap resolution; only 4.3.1 carries the fix. The intended security remediation is therefore incomplete for those dependency paths.

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