CVE-2026-67987 Denial of service in n/a
A malicious model response with many unterminated think tags causes excessive CPU consumption in the Ruby LLM library, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-67987?
CVE-2026-67987 is a high-severity denial of service vulnerability in n/a, published on 29 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
crmne/ruby_llm at commit fa6f279847d6d7027814539d9c0dfc3bbdfd2a83 contains polynomial-time regular expression denial-of-service conditions in think-tag response parsing on Ruby 3.1.x. A malicious or anomalous model response containing many unterminated <think> tags can cause excessive CPU consumption in two consecutive regular expressions and delay chat-completion processing
Weakness: CWE-1333
Which versions are affected by CVE-2026-67987?
How do I fix CVE-2026-67987?
No fix has been published for CVE-2026-67987 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-67987 being exploited?
There is no known exploitation of CVE-2026-67987 in the wild and no public exploit code.
Sources
Also known as GHSA-5m38-526f-3498, UBUNTU-CVE-2026-67987.