{"id":"CVE-2026-84375","state":"PUBLISHED","title":"js-yaml: maxTotalMergeKeys does not limit CPU use for empty merge sources","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.","publishedAt":"2026-09-01T21:43:13.617Z","updatedAt":"2026-09-28T21:32:39.387Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","source":"GitHub_M"},"assigner":"GitHub_M","products":["nodeca js-yaml"],"affected":[{"vendor":"nodeca","product":"js-yaml","versions":[{"version":">= 3.0.0, < 3.15.2","status":"affected"},{"version":">= 4.0.0, < 4.3.2","status":"affected"},{"version":">= 5.0.0, < 5.4.1","status":"affected"}]}],"references":["https://github.com/nodeca/js-yaml/security/advisories/GHSA-2883-xcg3-v3hh","https://github.com/nodeca/js-yaml/pull/797","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/releases/tag/3.15.2","https://github.com/nodeca/js-yaml/releases/tag/4.3.2","https://github.com/nodeca/js-yaml/releases/tag/5.4.1"],"weaknesses":["CWE-400","CWE-407"],"ingestedAt":"2026-10-29T20:13:15.269Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/84xxx/CVE-2026-84375.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-84375","state":"PUBLISHED","datePublished":"2026-09-01T21:43:13.617Z","dateUpdated":"2026-09-28T21:32:39.387Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-09-01T16:27:58.129Z"},"containers":{"cna":{"title":"js-yaml: maxTotalMergeKeys does not limit CPU use for empty merge sources","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"nodeca","product":"js-yaml","versions":[{"version":">= 3.0.0, < 3.15.2","status":"affected"},{"version":">= 4.0.0, < 4.3.2","status":"affected"},{"version":">= 5.0.0, < 5.4.1","status":"affected"}]}],"references":[{"url":"https://github.com/nodeca/js-yaml/security/advisories/GHSA-2883-xcg3-v3hh","name":"https://github.com/nodeca/js-yaml/security/advisories/GHSA-2883-xcg3-v3hh","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/nodeca/js-yaml/pull/797","name":"https://github.com/nodeca/js-yaml/pull/797","tags":["x_refsource_MISC"]},{"url":"https://github.com/nodeca/js-yaml/commit/3485bc06ff8a0251505f44a00414d90df2466639","name":"https://github.com/nodeca/js-yaml/commit/3485bc06ff8a0251505f44a00414d90df2466639","tags":["x_refsource_MISC"]},{"url":"https://github.com/nodeca/js-yaml/commit/6a8e05f9a485188ed730ac81e81ae221352ef480","name":"https://github.com/nodeca/js-yaml/commit/6a8e05f9a485188ed730ac81e81ae221352ef480","tags":["x_refsource_MISC"]},{"url":"https://github.com/nodeca/js-yaml/commit/d90b6612a5a84385bdcb556c44578eac76dc0f6b","name":"https://github.com/nodeca/js-yaml/commit/d90b6612a5a84385bdcb556c44578eac76dc0f6b","tags":["x_refsource_MISC"]},{"url":"https://github.com/nodeca/js-yaml/releases/tag/3.15.2","name":"https://github.com/nodeca/js-yaml/releases/tag/3.15.2","tags":["x_refsource_MISC"]},{"url":"https://github.com/nodeca/js-yaml/releases/tag/4.3.2","name":"https://github.com/nodeca/js-yaml/releases/tag/4.3.2","tags":["x_refsource_MISC"]},{"url":"https://github.com/nodeca/js-yaml/releases/tag/5.4.1","name":"https://github.com/nodeca/js-yaml/releases/tag/5.4.1","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-400","lang":"en","description":"CWE-400: Uncontrolled Resource Consumption","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-407","lang":"en","description":"CWE-407: Inefficient Algorithmic Complexity","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-09-28T21:32:39.387Z"},"source":{"advisory":"GHSA-2883-xcg3-v3hh","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-02T13:43:50.850378Z","id":"CVE-2026-84375","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-02T16:02:06.745Z"}}]}}}