Vulnerability · Published Jul 8, 2026 · Assigned by GitHub_M
CVE-2026-59868js-yaml: YAML merge-key chains can force quadratic CPU consumption
Medium 5.3
In plain English
A medium-severity security flaw in js-yaml from nodeca. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 51% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)5.3Medium
Exploit odds (30 days)0.6%top 48.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known
Official description
js-yaml is a JavaScript YAML parser and dumper. From 5.0.0 before 5.2.0, when merge keys are enabled, 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 version 5.2.0.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu:22.04:LTS | node-js-yaml | no fix listed | UBUNTU-CVE-2026-59868 |
| Ubuntu:24.04:LTS | node-js-yaml | no fix listed | UBUNTU-CVE-2026-59868 |
| Ubuntu:25.10 | node-js-yaml | no fix listed | UBUNTU-CVE-2026-59868 |
| Ubuntu:26.04:LTS | node-js-yaml | no fix listed | UBUNTU-CVE-2026-59868 |
| Ubuntu:26.10 | node-js-yaml | no fix listed | UBUNTU-CVE-2026-59868 |
| npm | js-yaml | 5.2.0 | GHSA-g796-fgmg-93mv |
Affected products (as reported)
Weakness: CWE-407 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
References
- https://github.com/nodeca/js-yaml/security/advisories/GHSA-g796-fgmg-93mv x_refsource_CONFIRM
- https://github.com/nodeca/js-yaml/commit/3105455b81dee69e0fd36e09ac0b2ccfdb54adc1 x_refsource_MISC
- https://github.com/nodeca/js-yaml/releases/tag/5.2.0 x_refsource_MISC