Regular Expression DoS in Ruby 3.1.x with Mistral Model Matching

Executive Summary

This vulnerability is a regular expression denial-of-service (ReDoS) issue in the ruby_llm gem's Mistral provider. It occurs when processing long model IDs containing repeated 'voxtral' strings without matching suffixes. The original regex patterns like /voxtral.*tts/ and /voxtral.*transcribe/ caused quadratic time complexity, making the system slow or unresponsive when handling such inputs.

Useful 0 Not Useful 0

Detection Guidance

This vulnerability is specific to the ruby_llm gem's Mistral provider and involves inefficient regex pattern matching in Ruby 3.1.x. To detect it, check if your application uses the ruby_llm gem version affected by CVE-2026-67989 and inspect model ID handling for Voxtral variants. Look for regex patterns like /voxtral.*tts/ or /voxtral.*transcribe/ in your codebase.

Useful 0 Not Useful 0

Impact Analysis

If you use the ruby_llm gem with Ruby 3.1.x and interact with Mistral AI models, an attacker could send a specially crafted model ID to trigger the ReDoS. This could cause your application to slow down significantly or become unresponsive, potentially leading to denial-of-service conditions in your system.

Useful 0 Not Useful 0

Mitigation Strategies

Update the ruby_llm gem to the latest version that includes the fix for CVE-2026-67989. Replace regex-based model ID checks with the new String#index-based methods (voxtral_followed_by? and voxtral_modalities_for) as shown in the patched capabilities.rb file.

Useful 0 Not Useful 0