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.
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History
Mon, 09 Nov 2026 17:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Title | Inefficient Algorithmic Complexity Causes Denial of Service in Eclipse Langium |
Mon, 09 Nov 2026 16:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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. | |
| Weaknesses | CWE-407 | |
| References |
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| Metrics |
cvssV4_0
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Status: PUBLISHED
Assigner: eclipse
Published:
Updated: 2026-11-09T16:47:45.873Z
Reserved: 2026-11-09T10:36:46.112Z
Link: CVE-2026-124683
No data.
Status : Received
Published: 2026-11-09T17:17:27.690
Modified: 2026-11-09T17:17:27.690
Link: CVE-2026-124683
No data.
OpenCVE Enrichment
Updated: 2026-11-09T18:00:18Z
Weaknesses