{"id":"CVE-2026-124683","published":"2026-11-09T17:17:27.690","lastModified":"2026-11-09T17:17:27.690","description":"Eclipse Langium versions 3.2.0 through 4.4.0 contain an inefficient algorithmic complexity issue (CWE-407) in the opt-in IndentationAwareTokenBuilder and IndentationAwareLexer. When producing DEDENT tokens, the token builder recomputes line numbers by re-scanning the entire preceding document text. A document whose indentation changes on most lines then takes quadratic time to tokenize. Because tokenization is synchronous, a crafted document of a few hundred kilobytes can block the Node.js event loop for tens of seconds. That causes a DoS for every user served by the same process. Languages built with the DefaultLexer and DefaultTokenBuilder are unaffected.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":["CWE-407"],"vendors":[],"products":[],"references":[{"url":"https://github.com/eclipse-langium/langium/security/advisories/GHSA-297v-g8mm-qj4h","tags":[]},{"url":"https://gitlab.eclipse.org/security/cve-assignment/-/work_items/553","tags":[]},{"url":"https://gitlab.eclipse.org/security/vulnerability-reports/-/work_items/1069","tags":[]}],"exploitRefs":[{"url":"https://github.com/eclipse-langium/langium/security/advisories/GHSA-297v-g8mm-qj4h","tags":[]}],"hasPoc":true,"ai":null}