{"id":"CVE-2026-73643","revision":null,"records":[{"revision":"f7a7b4b684424c28bd628d12cf4fcd9b","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-73643","aliases":[],"title":"js-yaml: Exponential parsing time in the flow collections leads to denial of service","description":"js-yaml is a JavaScript YAML parser and dumper. From 5.0.0 until 5.2.2, parsing a small YAML document can take exponential time when an application calls load() or loadAll() on untrusted input. In src/parser/parser.ts, readFlowCollection uses restoreState and calls parseNode a second time when a flow-sequence entry is recognized as a key: value pair. If the key is a nested flow sequence of the same shape, every level is parsed twice, causing O(2^n) work and allowing an input under 200 bytes to keep one CPU busy for minutes, block the Node.js event loop, and stall the process. No anchors, aliases, merges, tags, or nondefault options are required. This issue is fixed in version 5.2.2.","state":0,"publishedAt":"2026-08-13T17:47:30.404+00:00","modifiedAt":"2026-08-14T16:44:08.839+00:00","affected":[{"ecosystem":"Vendor product","name":"js-yaml","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"nodeca\",\n                    \"product\": \"js-yaml\",\n                    \"versions\": [\n                        {\n                            \"version\": \">= 5.0.0, < 5.2.2\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 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,"severity":"HIGH"}],"references":["https://github.com/nodeca/js-yaml/security/advisories/GHSA-pm4m-ph32-ghv5","https://github.com/nodeca/js-yaml/commit/3e5240f9cbe645ce5afb58524954a13c8539c853"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-73643","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-73643","identifiers":["CVE-2026-73643"]},"retained":false,"historicalAffected":[]},{"revision":"76c76a319f6b4c8ca6c3bf56a45dfce6","observedAt":"2026-10-25T15:19:09.409+00:00","statement":{"source":"nvd","id":"CVE-2026-73643","aliases":[],"title":"js-yaml is a JavaScript YAML parser and dumper. From 5.0.0 until 5.2.2, parsing a small YAML document can take exponential time when an application calls load() or loadAll() on untrusted input. In src/parser/parser.ts, readFlowCollection us…","description":"js-yaml is a JavaScript YAML parser and dumper. From 5.0.0 until 5.2.2, parsing a small YAML document can take exponential time when an application calls load() or loadAll() on untrusted input. In src/parser/parser.ts, readFlowCollection uses restoreState and calls parseNode a second time when a flow-sequence entry is recognized as a key: value pair. If the key is a nested flow sequence of the same shape, every level is parsed twice, causing O(2^n) work and allowing an input under 200 bytes to keep one CPU busy for minutes, block the Node.js event loop, and stall the process. No anchors, aliases, merges, tags, or nondefault options are required. This issue is fixed in version 5.2.2.","state":0,"publishedAt":"2026-08-13T18:18:19.947+00:00","modifiedAt":"2026-10-24T15:10:00.19+00:00","affected":[],"metrics":[{"system":"CVSS 3.1 · security-advisories@github.com · Secondary","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5,"severity":"HIGH"}],"references":["https://github.com/nodeca/js-yaml/commit/3e5240f9cbe645ce5afb58524954a13c8539c853","https://github.com/nodeca/js-yaml/security/advisories/GHSA-pm4m-ph32-ghv5"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-73643","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Deferred","weaknesses":["CWE-407"],"productCriteria":[],"sourceDates":{"published":"2026-08-13T18:18:19.947","lastModified":"2026-10-24T15:10:00.190"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-73643","identifiers":["CVE-2026-73643"]},"retained":false,"historicalAffected":[]},{"revision":"566f272f671446a2aea847d4a33605a3","observedAt":"2026-10-24T13:17:17.793+00:00","statement":{"source":"osv","id":"GHSA-pm4m-ph32-ghv5","aliases":["CVE-2026-73643"],"title":"js-yaml: Exponential parsing time in flow collections leads to denial of service","description":"### Summary\nParsing a small YAML document can take exponential time. An application that calls `load()` or `loadAll()` on untrusted input can be hung by a payload under 200 bytes.\n\n### Details\nWhen an entry in a flow sequence turns out to be a `key: value` pair, the parser rewinds and parses that entry a second time as the key.\nIf the key is itself a nested flow sequence of the same shape, every level is parsed twice, so the total work is O(2^n) in the nesting depth. The default `maxDepth` of 100 does not help, because the time is already unmanageable at about 30 to 40 levels.\n\nRoot cause, potentially the: `readFlowCollection` in [parser.ts](https://github.com/nodeca/js-yaml/blob/master/src/parser/parser.ts), the `restoreState` followed by a second `parseNode` further down.\n\n\n### PoC\n\n```javascript\nconst yaml = require('js-yaml')\nconst n = 30\nyaml.load('[ '.repeat(n) + '1' + ' ]: 0'.repeat(n))\n```\n\nWith default options: 22 levels takes about 1 second, 26 levels about 17 seconds, 30 levels over 2 minutes. The input stays under 200 bytes and grows linearly with `n`.\n\n### Impact\nDenial of service. A single small request can keep one CPU busy for minutes or longer and blocks the Node event loop, so one request can stall the whole process. No anchors, aliases, merges, tags, or non default options are required, and it reproduces on the default schema.","state":0,"publishedAt":"2026-07-24T16:47:36+00:00","modifiedAt":"2026-09-10T03:51:11.6524589+00:00","affected":[{"ecosystem":"npm","name":"js-yaml","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"5.0.0"},{"kind":"fixed","version":"5.2.2"}]}],"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:H","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"HIGH"}],"references":["https://github.com/nodeca/js-yaml/security/advisories/GHSA-pm4m-ph32-ghv5","https://github.com/nodeca/js-yaml/commit/3e5240f9cbe645ce5afb58524954a13c8539c853","https://github.com/nodeca/js-yaml","https://github.com/nodeca/js-yaml/releases/tag/5.2.2"],"sourceUrl":"https://github.com/advisories/GHSA-pm4m-ph32-ghv5","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-pm4m-ph32-ghv5","identifiers":["GHSA-pm4m-ph32-ghv5","CVE-2026-73643"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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