chore(deps): update dependency js-yaml@<3.15.0 to v5 [security]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
js-yaml@<3.15.0	^3.15.0 → ^5.0.0

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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).

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Release Notes

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

v5.3.0

Compare Source

This release focuses on reworking the documentation and making small
architectural improvements before moving forward.

Added

• Added completely new documentation.
• Exported DUMP_SCHEMA, the default schema used by the dumper.
• Added YAMLException.throwAt() for throwing an error at a source position.

Changed

• Changed flat constant exports to grouped exports: EVENT_ID, SCALAR_STYLE,
  COLLECTION_STYLE, and CHOMPING_MODE, along with their value types. The old
  exports are still preserved, but deprecated.
• Made identify mandatory for custom tag definitions. Use
  identify: () => false for load-only tags.

Deprecated

• Deprecated flat constant exports. Use grouped ones instead.

Removed

• Removed the MERGE_KEY export (not used anymore after last fixes).

Fixed

• Validate << sequence items at merge time, so aliased merge sources are
  checked too.
• Resolve << outside of a mapping key as the plain string '<<', matching
  v4, instead of leaking an internal symbol into the result.

v5.2.3

Compare Source

Fixed

• Prevent prototype fallback when resolving tags and mapping entries, #​782.
• Resolve !!timestamp years 0000-0099 correctly, #​775.
• Preserve implicit null mapping values before document markers and reject
  unpaired mapping event streams, #​784.
• Preserve folded scalar values with tab-indented lines when round-tripping a
  parsed AST through present(); dump() and loading are unaffected, #​780.

v5.2.2

Compare Source

Fixed

• Quote flow scalars where a colon precedes a flow indicator, #​773.

Security

• Avoid exponential parsing time for nested flow sequence pairs.

v5.2.1

Compare Source

Fixed

• Add Map support to !!omap (should work when realMapTag used)

Security

• Remove quadratic complexity from !!omap addItem. Regression from v5
  (usually not critical, because YAML11_SCHEMA is not default anymore).

v5.2.0

Compare Source

Added

• Added maxTotalMergeKeys (10000) loader option to limit the total number of
  keys processed by YAML merge (<<) across one load() / loadAll() call.
• Added maxAliases (-1) loader option to limit the number of YAML aliases per
  document.

Removed

• maxMergeSeqLength replaced with maxTotalMergeKeys for limiting YAML merge
  processing.

Fixed

• Round-trip of integers with exponential form (>= 1e21)

v5.1.0

Compare Source

Added

• Collection tags can finalize an incrementally populated carrier into a
  different result value.

Changed

• [breaking] quoteStyle now selects the preferred quote style; use the
  restored forceQuotes option to force quoting non-key strings.

v5.0.0

Compare Source

Added

• Added named exports for schemas, tags, parser events and AST utilities.
• Reworked JSON_SCHEMA and CORE_SCHEMA with spec-compliant scalar resolution
  rules, and added YAML11_SCHEMA.
• Added realMapTag for lossless mappings with non-string and complex keys.
  Object-based mappings now reject complex keys instead of stringifying them.
• Added dump() transform option for changing the generated AST before
  rendering.
• Added dump() options seqInlineFirst, flowBracketPadding,
  flowSkipCommaSpace, flowSkipColonSpace, quoteFlowKeys, quoteStyle and
  tagBeforeAnchor.
• Added formal data layers (events and AST) for modular data pipelines.
  • Added low-level parser (to events), presenter and visitor APIs.
• Added the YAML Test Suite to the
  test set.

Changed

• See the migration guide for upgrade notes.
• Rewritten in TypeScript and reorganized the public API around flat named
  exports.
• Reduced the set of exported schemas:
  • YAML 1.2 schemas: CORE_SCHEMA (loader default), JSON_SCHEMA,
    FAILSAFE_SCHEMA.
  • YAML11_SCHEMA, a combination of all YAML 1.1 tags (YAML 1.1 does not
    specify a schema, only "types").
• load/dump default behaviour is now specified exactly via schemas:
  • load uses CORE_SCHEMA, without !!merge by default.
  • dump uses YAML11_SCHEMA + CORE_SCHEMA for the quoting check, to
    guarantee backward compatibility by default.
• !!set is now loaded as a JavaScript Set.
• Replaced the Type API with a tags API. Similar, but more precise and
  simpler. See examples for details. Tags can be defined via
  defineScalarTag(), defineSequenceTag() and defineMappingTag(), or as a
  spread + override of an existing tag.
• Renamed Schema.extend() to Schema.withTags().
• Expanded YAML 1.2 conformance and improved handling of directives, document
  markers, block keys, multiline scalars, tag syntax and other things.
• load() now throws on empty input instead of returning undefined.
• Moved browser builds to the js-yaml/browser export.
• Deprecated the loadAll signature with an iterator (still works, but is a
  candidate for removal).

Removed

• Removed deprecated safeLoad(), safeLoadAll() and safeDump() exports.
• Removed DEFAULT_SCHEMA and the nested types export.
• Removed loader options onWarning, legacy and listener.
• Removed dumper options styles, replacer, noCompatMode, condenseFlow,
  quotingType and forceQuotes. Renamed noArrayIndent to seqNoIndent.
  Formatting and representation are now configured through presenter options,
  schemas and tag definitions. See migration guide on how to replace.
• Removed support for importing internal files from lib/.

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.

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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 tooling crashes because a YAML helper is forced onto an incompatible library version

The old YAML library used by the release tooling is replaced with a version 5 release ('js-yaml@<3.15.0': ^5.0.0 at pnpm-workspace.yaml:42) even though the helper still calls a function that only exists in version 3, so changeset/versioning commands crash.
Impact: Running the changesets release/version commands fails with a runtime error, blocking publishing.

Mechanism: read-yaml-file calls yaml.safeLoad, removed in js-yaml 4/5

@manypkg/get-packages@1.1.3 (a dependency of @changesets/cli) depends on read-yaml-file@1.1.0, whose entire implementation is const parse = data => yaml.safeLoad(stripBom(data)) and which declares js-yaml: ^3.6.1. The override widens that to ^5.0.0, and the lockfile now resolves read-yaml-file@1.1.0 → js-yaml: 5.3.0 (pnpm-lock.yaml:9014-9019). js-yaml removed safeLoad in v4 (verified: require('js-yaml@5.3.0').safeLoad === undefined), so any workspace/package YAML read by changesets throws TypeError: yaml.safeLoad is not a function.

A safer scope would keep the 3.x consumers on a 3.x-compatible line (or pin read-yaml-file to a newer major that uses load), rather than forcing the pre-3.15 range straight to v5.

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