CVE-2026-9540 vllm-project vllm OpenAI-compatible Serving Path denial of service
Remote attackers can cause denial of service in vLLM's OpenAI-compatible serving path via a publicly available exploit.
- 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-2026-9540?
CVE-2026-9540 is a medium-severity denial of service vulnerability in vllm-project vllm, published on 26 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
A vulnerability was identified in vllm-project vllm 0.19.0. This issue affects some unknown processing of the component OpenAI-compatible Serving Path. Such manipulation leads to denial of service. It is possible to launch the attack remotely. The exploit is publicly available and might be used. The pull request to fix this issue awaits acceptance.
Weakness: CWE-404
Which versions are affected by CVE-2026-9540?
3 open source packages ship an affected version, including vllm.
| Package | Affected | Fixed in |
|---|---|---|
vllm PyPI | All versions to 0.19.0 | None |
vllm PyPI | All versions to 0.19.0 | None |
vllm PyPI | All versions to 0.19.0 | None |
How do I fix CVE-2026-9540?
No fix has been published for CVE-2026-9540 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-2026-9540 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-9540 exists.
Sources
Also known as GHSA-98f3-hwg4-4rf7, PYSEC-2026-3407.