CVE-2026-53550
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.
- CVSS 3.1
- 5.3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - EPSS
- 0.4% chance of exploitation in the next 30 days; higher than 35% of CVEs (scores of 2026-10-25)
- CWE
- CWE-407
- Published
- Modified
- Record from
- the NVD, synced
Affected
- nodeca:js-yaml
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-h67p-54hq-rp68 | npm | js-yaml | >=4.0.0 <4.2.0 | 4.2.0 |
| GHSA-h67p-54hq-rp68 | npm | js-yaml | <3.15.0 | 3.15.0 |