Vulnerability · Published Oct 26, 2026 · Assigned by GitHub_M
CVE-2026-115911vLLM: DoS via unbounded chat_template Jinja2 rendering exhausts the renderer thread pool
Medium 6.5
In plain English
A medium-severity uncontrolled resource consumption in vllm from vllm-project. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 24% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| PyPI | vllm | 0.32.0 | GHSA-542m-9234-8gvf |
| PyPI | vllm | 0.32.0 | PYSEC-2026-4344 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| vllm-project | vllm | >= 0.19.0, < 0.32.0 |
Weakness: CWE-400, CWE-770, CWE-834 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
References
- https://github.com/vllm-project/vllm/security/advisories/GHSA-542m-9234-8gvf x_refsource_CONFIRM
- https://github.com/vllm-project/vllm/pull/50300 x_refsource_MISC
- https://github.com/vllm-project/vllm/commit/cff08b461e086523cee8bba5bd3c66d302625134 x_refsource_MISC
- https://github.com/vllm-project/vllm/releases/tag/v0.32.0 x_refsource_MISC