Vulnerability in Nodeca Js-Yaml
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
EPSS: 0.004 (33.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 33rd percentile — 33.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: +0.000
Affected products
- Nodeca Js-Yaml — versions < 3.15.0, >= 4.0.0, < 4.2.0, < 4.2.0
Weakness classification (CWE)
References
- github.com/nodeca/js-yaml/security/advisories/GHSA-h67p-54hq-rp68 (Exploit, Mitigation, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-53550?
- CVE-2026-53550 is a medium-severity vulnerability in Nodeca Js-Yaml, classified under Inefficient Algorithmic Complexity. CVSS score: 5.3/10. Published 2026-06-22.
- How severe is CVE-2026-53550?
- Medium severity. CVSS v3 base score is 5.3 out of 10.