Vulnerability · Published Jun 22, 2026 · Assigned by GitHub_M
CVE-2026-53550js-yaml: Quadratic-complexity DoS in merge key handling via repeated aliases
Medium 5.3
In plain English
A medium-severity security flaw in js-yaml from nodeca. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 36% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
js-yaml is a JavaScript YAML parser and dumper. Prior to 4.2.0 and 3.15.0, a crafted YAML document can trigger algorithmic CPU exhaustion in js-yaml merge-key processing (<<) by repeating the same alias many times in a merge sequence. This causes quadratic parse-time behavior relative to input size and can block a Node.js worker/event loop for seconds with a relatively small payload (tens of KB), resulting in denial of service. The issue is in merge handling inside lib/loader.js. This vulnerability is fixed in 4.2.0 and 3.15.0.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | node-js-yaml | no fix listed | DEBIAN-CVE-2026-53550 |
| Debian:13 | node-js-yaml | no fix listed | DEBIAN-CVE-2026-53550 |
| Debian:14 | node-js-yaml | 4.2.0+~4.0.9-1 | DEBIAN-CVE-2026-53550 |
| Ubuntu:22.04:LTS | node-js-yaml | no fix listed | UBUNTU-CVE-2026-53550 |
| Ubuntu:24.04:LTS | node-js-yaml | no fix listed | UBUNTU-CVE-2026-53550 |
| Ubuntu:25.10 | node-js-yaml | no fix listed | UBUNTU-CVE-2026-53550 |
| Ubuntu:26.04:LTS | node-js-yaml | no fix listed | UBUNTU-CVE-2026-53550 |
| Ubuntu:26.10 | node-js-yaml | no fix listed | UBUNTU-CVE-2026-53550 |
| npm | js-yaml | 4.2.0 | GHSA-h67p-54hq-rp68 |
| npm | js-yaml | 3.15.0 | GHSA-h67p-54hq-rp68 |
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-h67p-54hq-rp68 x_refsource_CONFIRM