{"id":"CVE-2026-124683","details":"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.","aliases":["GHSA-297v-g8mm-qj4h"],"modified":"2026-11-10T02:41:16.474466Z","published":"2026-11-09T16:02:50.370Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/124xxx/CVE-2026-124683.json","cna_assigner":"eclipse","cwe_ids":["CWE-407"]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/124xxx/CVE-2026-124683.json"},{"type":"ADVISORY","url":"https://github.com/eclipse-langium/langium/security/advisories/GHSA-297v-g8mm-qj4h"},{"type":"WEB","url":"https://gitlab.eclipse.org/security/cve-assignment/-/work_items/553"},{"type":"WEB","url":"https://gitlab.eclipse.org/security/vulnerability-reports/-/work_items/1069"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-124683"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/eclipse-langium/langium","events":[{"introduced":"b2a6fe9684434117eb6a344fc2721e3c26d989bf"},{"last_affected":"89d49680b39218af2e5b700cd3f4fdc122600ac4"}],"database_specific":{"extracted_events":[{"strategy":"StandardRange","range":[{"introduced":"3.2.0"},{"last_affected":"4.4.0"}],"source":"AFFECTED_FIELD"}]}}],"versions":["v4.4.0","v4.3.0","v4.2.0","v4.1.0","v4.0.0","v3.5.0","v3.4.0","v3.3.1","v3.2.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-124683.json"}}],"schema_version":"1.9.2","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"}]}