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VulnerabilityPublished

CVE-2026-124683: Eclipse Langium · Inefficient Algorithmic Complexity

Affects Eclipse LangiumSource CVE Database V5

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Not known to be exploited · CVSS 8.7 High.

Data as of 9 Nov 2026, 16:48 UTC

CVSS 4.0 base score
8.7High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (eclipse)CVSS 4.08.7
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 9 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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

ProductAffectedFixed in
Eclipse FoundationEclipse LangiumAffected
  • >=3.2.0 <=4.4.0
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.

References

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