CVE-2026-6607 lm-sys fastchat Worker API Endpoint api_generate resource consumption
Remote attackers can cause resource exhaustion in the fastchat Worker API, 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-2026-6607?
CVE-2026-6607 is a medium-severity denial of service vulnerability in lm-sys fastchat, published on 20 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
A security vulnerability has been detected in lm-sys fastchat up to 0.2.36. This issue affects the function api_generate of the component Worker API Endpoint. The manipulation leads to resource consumption. The attack can be initiated remotely. The exploit has been disclosed publicly and may be used. The identifier of the patch is c9e84b89c91d45191dc24466888de526fa04cf33. It is suggested to install a patch to address this issue. Commit ff66426 patched this issue in api_generate of base_model_worker.py and did miss other entry points.
Which versions are affected by CVE-2026-6607?
3 open source packages ship an affected version, including fschat.
| Package | Affected | Fixed in |
|---|---|---|
fschat PyPI | All versions to 0.2.26 | None |
fschat PyPI | All versions to 0.2.26 | None |
fschat PyPI | All versions to 0.2.26 | None |
How do I fix CVE-2026-6607?
No fix has been published for CVE-2026-6607 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-2026-6607 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-6607 exists.
Sources
Also known as GHSA-5h65-jx66-j7p5, PYSEC-2026-2484.