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Description

js-yaml is a JavaScript YAML parser and dumper. From 3.0.0 before 3.15.0 and from 4.0.0 before 4.3.0, js-yaml can spend quadratic CPU time parsing a document whose size grows only linearly when a chain of mappings uses merge keys where each mapping merges the previous one. This issue is fixed in versions 3.15.0 and 4.3.0.

PUBLISHED Reserved 2026-07-07 | Published 2026-07-08 | Updated 2026-07-09 | Assigner GitHub_M




HIGH: 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Problem types

CWE-407: Inefficient Algorithmic Complexity

Product status

>= 3.0.0, < 3.15.0
affected

>= 4.0.0, < 4.3.0
affected

References

github.com/...s-yaml/security/advisories/GHSA-52cp-r559-cp3m exploit

github.com/...s-yaml/security/advisories/GHSA-52cp-r559-cp3m

github.com/...ommit/24f13e79ee1343a7e30bd6f6c9d9cdbf0ac9b2b7

github.com/...ommit/59423c6f8cdc78742ac00e25a4dd39ef16b702e4

github.com/nodeca/js-yaml/releases/tag/3.15.0

github.com/nodeca/js-yaml/releases/tag/4.3.0

cve.org (CVE-2026-59869)

nvd.nist.gov (CVE-2026-59869)

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