CVE-2026-85695 FastChat Unauthenticated Worker Registration SSRF and Model Spoofing
Unauthenticated attackers can register malicious workers to intercept user data and perform server-side request forgery in FastChat deployments.
- 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-2026-85695?
CVE-2026-85695 is a critical server-side request forgery vulnerability in lm-sys FastChat, published on 4 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
FastChat contains an authentication bypass vulnerability in the /register_worker endpoint that allows unauthenticated attackers to register arbitrary worker addresses and perform server-side request forgery. Attackers can register malicious workers under victim model names to intercept user prompts, images, and responses, or probe internal network ports across the worker mesh.
Weakness: CWE-306
Which versions are affected by CVE-2026-85695?
How do I fix CVE-2026-85695?
No fix has been published for CVE-2026-85695 yet. Limit exposure of the affected software until one is available.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-85695 being exploited?
There is no known exploitation of CVE-2026-85695 in the wild and no public exploit code.
Sources
Also known as GHSA-46fr-7j3v-277v.