---
id: CVE-2026-67991
title: >-
  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
summary: >-
  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 ca…
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N'
cwe:
  - CWE-1333
published: '2026-08-13'
updated: '2026-09-08'
sourceUpdated: '2026-09-08T19:42:20.313'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-67991'
references:
  - url: 'https://gist.github.com/Zykis1024/9f2d68fa3fd4e3a0ab83063bbe61a8e2'
    label: cve@mitre.org
  - url: 'https://github.com/crmne/ruby_llm'
    label: cve@mitre.org
  - url: >-
      https://github.com/crmne/ruby_llm/blob/fa6f279847d6d7027814539d9c0dfc3bbdfd2a83/lib/ruby_llm/utils.rb#L13
    label: cve@mitre.org
  - url: >-
      https://github.com/crmne/ruby_llm/commit/9d75b033d7d00c4e1baa9b0afb4828faa8bd6602
    label: cve@mitre.org
tags:
  - nvd
epss: 0.00508
epssPercentile: 0.40916
ingestedAt: '2026-09-05T16:41:56.898Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.