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chore(deps): update dependency js-yaml@<=4.1.1 to v5 [security] - #1211

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chore(deps): update dependency js-yaml@<=4.1.1 to v5 [security]#1211
renovate[bot] merged 1 commit into
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renovate/npm-js-yaml-=4.1.1-vulnerability

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This PR contains the following updates:

Package Change Age Confidence
js-yaml@<=4.1.1 ^4.3.0^5.2.2 age confidence

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js-yaml: Exponential parsing time in flow collections leads to denial of service

GHSA-pm4m-ph32-ghv5

More information

Details

Summary

Parsing a small YAML document can take exponential time. An application that calls load() or loadAll() on untrusted input can be hung by a payload under 200 bytes.

Details

When an entry in a flow sequence turns out to be a key: value pair, the parser rewinds and parses that entry a second time as the key.
If the key is itself a nested flow sequence of the same shape, every level is parsed twice, so the total work is O(2^n) in the nesting depth. The default maxDepth of 100 does not help, because the time is already unmanageable at about 30 to 40 levels.

Root cause, potentially the: readFlowCollection in parser.ts, the restoreState followed by a second parseNode further down.

PoC
const yaml = require('js-yaml')
const n = 30
yaml.load('[ '.repeat(n) + '1' + ' ]: 0'.repeat(n))

With default options: 22 levels takes about 1 second, 26 levels about 17 seconds, 30 levels over 2 minutes. The input stays under 200 bytes and grows linearly with n.

Impact

Denial of service. A single small request can keep one CPU busy for minutes or longer and blocks the Node event loop, so one request can stall the whole process. No anchors, aliases, merges, tags, or non default options are required, and it reproduces on the default schema.

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

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


Release Notes

nodeca/js-yaml (js-yaml@<=4.1.1)

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/.

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@renovate renovate Bot added the dependencies Pull requests that update a dependency file label Jul 28, 2026
@renovate
renovate Bot merged commit 4551a0c into master Jul 28, 2026
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@renovate
renovate Bot deleted the renovate/npm-js-yaml-=4.1.1-vulnerability branch July 28, 2026 13:47
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