AIKIDO-2026-631276
vllm is vulnerable to Regular Expression Denial of Service (ReDoS)
53
CVE Score
Medium
Regular Expression Denial of Service (ReDoS)
TL;DR
The lm-format-enforcer structured-output backend compiles a user-supplied regular expression into a finite-state machine without a compile timeout or buildability check. A single request containing a catastrophic pattern pegs a CPU core during grammar compilation and stalls the structured-output engine path. This blocks concurrent requests and causes denial of service. The fix routes the compile through the same timeout guard already applied to the other structured-output backends.
How do I fix this?
Upgrade the vllm library to the patch version.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and you have selected the lm-format-enforcer structured outputs backend and accept user-controlled regular expressions.
Package
Versions
0.10.2 - 0.25.1
Fixed in 0.26.0Background info
vllm is vulnerable to Regular Expression Denial of Service (ReDoS) in versions 0.10.2 - 0.25.1.
Links
GitHub Release
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