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chore(deps): update dependency js-yaml to v4.3.2 [security] - #5286

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@renovate renovate Bot commented Sep 10, 2026

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This PR contains the following updates:

Package Change Age Confidence
js-yaml 4.3.14.3.2 age confidence

js-yaml: maxTotalMergeKeys does not limit CPU use for empty merge sources

CVE-2026-84375 / GHSA-2883-xcg3-v3hh

More information

Details

Summary

maxTotalMergeKeys does not count empty mappings. An attacker can repeatedly merge a large sequence of them and consume significant CPU without reaching the configured limit.

Example
arr: &arr [{}, {}, {}, ...] # N empty mappings
targets:
  - <<: *arr                # repeated K times

For every target, the loader iterates all N elements of arr. This results in O(N * K) work while totalMergeKeys remains unchanged.

PoC
import { performance } from 'node:perf_hooks'
import { load, YAML11_SCHEMA } from 'js-yaml'

const n = 20000

const src =
  'arr: &arr [' + '{},'.repeat(n).slice(0, -1) + ']\n' +
  'targets:\n' +
  '  - <<: *arr\n'.repeat(n)

const started = performance.now()

load(src, { schema: YAML11_SCHEMA })

console.log(`${(performance.now() - started).toFixed(1)} ms`)

Observed results:

N YAML size Time
800 ~13 KB ~20 ms
3200 ~50 KB ~180 ms
20000 ~500 KB ~13 s
Impact

An attacker can submit a relatively small YAML document that causes prolonged CPU consumption despite the default maxTotalMergeKeys limit.

Fix

Count each merge-source mapping as one budget unit, in addition to counting its keys.

Difference with v5

In v3 & v4, merge is enabled by default. So, the severity score is higher.

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)

v4.3.2

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@codecov

codecov Bot commented Sep 10, 2026

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 34.92%. Comparing base (afb16dc) to head (a4d3576).

Additional details and impacted files
@@           Coverage Diff           @@
##           master    #5286   +/-   ##
=======================================
  Coverage   34.92%   34.92%           
=======================================
  Files         741      741           
  Lines       23804    23804           
  Branches     6429     6429           
=======================================
  Hits         8314     8314           
  Misses      13746    13746           
  Partials     1744     1744           
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