CVE-2026-124683: Eclipse Langium · Inefficient Algorithmic Complexity
Affects Eclipse LangiumSource CVE Database V5
Not known to be exploited · CVSS 8.7 High.
Data as of 9 Nov 2026, 16:48 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
Users should avoid using the opt-in IndentationAwareTokenBuilder and IndentationAwareLexer with documents that have frequent indentation changes until a fix is available. Consider using the unaffected DefaultLexer and DefaultTokenBuilder as a workaround. Monitor the Eclipse Foundation advisories for updates and patches addressing this issue.
Description
Eclipse Langium versions 3.2.0 through 4.4.0 have an inefficient algorithmic complexity vulnerability (CWE-407) in the IndentationAwareTokenBuilder and IndentationAwareLexer. The issue causes quadratic time tokenization when processing documents with frequent indentation changes, leading to blocking of the Node.js event loop and denial of service. Languages using the default lexer and token builder are not affected.