CVE-2026-53550
js-yaml: Quadratic-complexity DoS in merge key handling via repeated aliases
Description
js-yaml is a JavaScript YAML parser and dumper. Prior to 4.2.0, 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.
INFO
Published Date :
June 22, 2026, 2:59 p.m.
Last Modified :
June 22, 2026, 2:59 p.m.
Remotely Exploit :
No
Source :
GitHub_M
Solution
- Update js-yaml to version 4.2.0 or later.
- Ensure merge-key processing is handled safely.
- Monitor resource usage for YAML parsing.
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