Eclipse Langium versions 3.2.0 through 4.4.0 contain an inefficient algorithmic complexity issue in the
Source GCVE Database
Not known to be exploited · CVSS 8.7 High.
Data as of 9 Nov 2026, 19:20 UTC
Thin evidence
One scorer or none| CNA (eclipse) | CVSS 4.0 | 8.7 |
|---|
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 9 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 9 Nov 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Eclipse FoundationEclipse Langium | Affected
| Fixed in– |
AI-suggested
Until a fix is available, avoid using the opt-in IndentationAwareTokenBuilder and IndentationAwareLexer with documents that have frequent indentation changes or limit document size to reduce the risk of event loop blocking.
Description
Eclipse Langium versions 3.2.0 through 4.4.0 have an inefficient algorithmic complexity issue in the opt-in IndentationAwareTokenBuilder and IndentationAwareLexer components. The issue causes tokenization to take quadratic time for documents with frequent indentation changes, blocking the Node.js event loop and resulting in a denial of service. Languages using the default lexer and token builder are not affected.
References
- github.com/eclipse-langium/langium/security/advisories/GHSA-297v-g8mm-qj4h (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-124683 (opens in a new tab)
- gitlab.eclipse.org/security/cve-assignment/-/work_items/553 (opens in a new tab)
- gitlab.eclipse.org/security/vulnerability-reports/-/work_items/1069 (opens in a new tab)