{"id":"CVE-2026-84375","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-84375","generatedAt":"2026-10-28T07:24:55.938Z","title":"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.","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.","published":"2026-09-01T22:17:19.000Z","lastModified":"2026-09-28T22:17:33.000Z","status":"Deferred","sourceIdentifier":"security-advisories@github.com","cvss":{"version":"3.1","score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"cwe":["CWE-400","CWE-407"],"affected":[],"epss":{"score":0.00541,"percentile":0.45297,"date":"2026-10-27","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.54%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"https://github.com/nodeca/js-yaml/commit/3485bc06ff8a0251505f44a00414d90df2466639","source":"security-advisories@github.com"},{"url":"https://github.com/nodeca/js-yaml/commit/6a8e05f9a485188ed730ac81e81ae221352ef480","source":"security-advisories@github.com"},{"url":"https://github.com/nodeca/js-yaml/commit/d90b6612a5a84385bdcb556c44578eac76dc0f6b","source":"security-advisories@github.com"},{"url":"https://github.com/nodeca/js-yaml/pull/797","source":"security-advisories@github.com"},{"url":"https://github.com/nodeca/js-yaml/releases/tag/3.15.2","source":"security-advisories@github.com"},{"url":"https://github.com/nodeca/js-yaml/releases/tag/4.3.2","source":"security-advisories@github.com"},{"url":"https://github.com/nodeca/js-yaml/releases/tag/5.4.1","source":"security-advisories@github.com"},{"url":"https://github.com/nodeca/js-yaml/security/advisories/GHSA-2883-xcg3-v3hh","source":"security-advisories@github.com"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-84375","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}