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.
Published: 2026-11-09
Score: 8.7 High
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

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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
Metrics cvssV4_0

{'score': 8.7, 'vector': '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'}


Subscriptions

No data.

cve-icon MITRE

Status: PUBLISHED

Assigner: eclipse

Published:

Updated: 2026-11-09T16:47:45.873Z

Reserved: 2026-11-09T10:36:46.112Z

Link: CVE-2026-124683

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-11-09T17:17:27.690

Modified: 2026-11-09T17:17:27.690

Link: CVE-2026-124683

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-11-09T17:30:08Z

Weaknesses