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Vulnerability record · CVE-2026-67991 · published 13 August 2026

CVE-2026-67991: Inefficient regular expression (ReDoS) vulnerability

crmne/ruby_llm at commit fa6f279847d6d7027814539d9c0dfc3bbdfd2a83 contains a polynomial-time regular expression denial-of-service condition in RubyLLM::Utils.underscore on Ruby 3.1.x. A very long crafted class, agent, or tool name can cause excessive CPU consumption and a denial of service.

7.5 CVSS 3.1 High EPSS 0.51% · top 59.0% CWE-1333 · Inefficient regular expression (ReDoS) Deferred
7.5CVSS 3.1 base score
0.51%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
4References
8 Sep 2026Last modified by NVD

Description

crmne/ruby_llm at commit fa6f279847d6d7027814539d9c0dfc3bbdfd2a83 contains a polynomial-time regular expression denial-of-service condition in RubyLLM::Utils.underscore on Ruby 3.1.x. A very long crafted class, agent, or tool name can cause excessive CPU consumption and a denial of service.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

References

LinkTags
https://gist.github.com/Zykis1024/9f2d68fa3fd4e3a0ab83063bbe61a8e2
https://github.com/crmne/ruby_llm
https://github.com/crmne/ruby_llm/blob/fa6f279847d6d7027814539d9c0dfc3bbdfd2a83/lib/ruby_llm/utils.rb#L13
https://github.com/crmne/ruby_llm/commit/9d75b033d7d00c4e1baa9b0afb4828faa8bd6602

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Source: NIST National Vulnerability Database (record CVE-2026-67991), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.