{"cve":"CVE-2026-84375","nvd":{"published":"2026-09-01T22:17:19.440","modified":"2026-09-28T22:17:33.377","status":"Deferred","description":"js-yaml is a JavaScript YAML parser and dumper. From 3.0.0 until 3.15.2, 4.3.2, and 5.4.1, maxTotalMergeKeys in lib/js-yaml/loader.js and lib/loader.js does not count empty mapping sources while processing the merge key <<. An attacker can alias a large sequence of empty mappings into many merge targets, causing O(N * K) processing while totalMergeKeys remains unchanged and the configured resource limit is never reached. A relatively small YAML document can therefore cause prolonged CPU consumption in applications that parse untrusted YAML, and merge processing is enabled by default on these release lines. In v3 & v4, merge is enabled by default so the severity score is higher. This issue is fixed in versions 3.15.2, 4.3.2, and 5.4.1.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-400","CWE-407"],"references":["https://github.com/nodeca/js-yaml/commit/3485bc06ff8a0251505f44a00414d90df2466639","https://github.com/nodeca/js-yaml/commit/6a8e05f9a485188ed730ac81e81ae221352ef480","https://github.com/nodeca/js-yaml/commit/d90b6612a5a84385bdcb556c44578eac76dc0f6b","https://github.com/nodeca/js-yaml/pull/797","https://github.com/nodeca/js-yaml/releases/tag/3.15.2"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:50:50.842544443+00:00"},"epss":{"cve":"CVE-2026-84375","score":0.00541,"percentile":0.45507,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-2883-xcg3-v3hh","url":"https://osv.dev/vulnerability/GHSA-2883-xcg3-v3hh","summary":"js-yaml: maxTotalMergeKeys does not limit CPU use for empty merge sources","modified":"2026-09-08T21:30:05.575808098Z","packages":[{"ecosystem":"npm","name":"js-yaml","purl":"pkg:npm/js-yaml","ranges":[">=4.0.0 <4.3.2"],"fixed":["4.3.2"]},{"ecosystem":"npm","name":"js-yaml","purl":"pkg:npm/js-yaml","ranges":[">=3.0.0 <3.15.2"],"fixed":["3.15.2"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}