vLLM: DoS via unbounded chat_template Jinja2 rendering exhausts the renderer thread pool

[ Description ]Official description

vLLM is an inference and serving engine for large language models. From 0.19.0 until 0.32.0, authenticated callers can supply a request chat template when no server-side --chat-template is configured, or a malicious model repository can provide a template that is compiled and rendered by tokenizer.apply_chat_template() without a wall-clock timeout, output-size limit, or iteration bound. Rendering runs in a ThreadPoolExecutor with one worker by default, so a nonterminating render can block /v1/responses and other chat-template users after the request ends, while an output-expanding render can exhaust server memory. Harmony models are not affected because they do not use this Jinja path. This issue is fixed in version 0.32.0.

[ Fixes ]Fixes and patches

• vllm 0.32.0Fixed version · GitHub Advisories · pip package vllm: upgrade to 0.32.0 or later (affected >= 0.19.0, < 0.32.0)
• Patch on github.comVendor patch or bulletin · NVD · Reference tagged 'Patch' by NVD
• Patch on github.comVendor patch or bulletin · NVD · Reference tagged 'Patch' by NVD
• Patch on github.comVendor patch or bulletin · NVD · Reference tagged 'Patch' by NVD

[ Advisories ]Government CERT advisories

• BSI CERT-Bund19 Oct 2026WID-SEC-2026-4051

  vllm: Multiple vulnerabilities Translated from German

  CVE-2026-115918CVE-2026-115911CVE-2026-115912+6 more CVEs

[ Packages ]Affected open-source packages

• vllm pipAffected >= 0.19.0, < 0.32.0 · fixed in 0.32.0 · GHSA-542m-9234-8gvf

[ References ]References

• github.com/vllm-project/vllm/commit/cff08b461e086523cee8bba5bd3c66d302625134Patch
• github.com/vllm-project/vllm/pull/50300Patch
• github.com/vllm-project/vllm/releases/tag/v0.32.0Release Notes
• github.com/vllm-project/vllm/security/advisories/GHSA-542m-9234-8gvfPatchVendor Advisory