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Advisory record · GHSA-r3ph-w7gj-g6xm

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

CVSS 5.3 Medium

Published by the GitHub Advisory Database at 29 Sept 2026, 17:57 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

PackageEcosystemAffectedFixed in
js-yamlnpm>=5.0.0, <5.4.15.4.1
Identifiers
GHSA-r3ph-w7gj-g6xm
Weakness (CWE)
CWE-400 · CWE-407
Tags
Published
29 Sept 2026
Updated
29 Sept 2026

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

The js-yaml package, versions 5.0.0 up to but not including 5.4.1, does not count empty mappings toward its maxTotalMergeKeys limit when parsing YAML merge keys. An attacker who can supply YAML for parsing could use a modest-sized document with many repeated merges of empty mappings to force prolonged CPU use, despite the configured limit. Upgrade to js-yaml 5.4.1, which is the listed fixed version.

Written 31 Oct 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

ScoreRatingCVSSVectorSource
5.3 Medium 3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L GitHub Advisory Database
  • CISA KEV Not listed.
  • EPSS No score.

Timeline

  1. 31 Oct 2026, 13:34 UTC First seen by agentprime
  2. 31 Oct 2026, 13:34 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.