CVE-2026-85695
9.3
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N
Summary
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.
Affected Software
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| lm-sys | FastChat | 0 <= 0.2.36 | affected |
Weaknesses
- CWE-306: Missing Authentication for Critical Function
ADP Enrichment
CISA ADP Vulnrichment
- SSVC:
- Exploitation: none
- Automatable: yes
- Technical Impact: total
References
- https://github.com/lm-sys/FastChat/issues/3886
- https://github.com/lm-sys/FastChat
- https://github.com/lm-sys/FastChat/blob/v0.2.36/fastchat/serve/controller.py
- https://www.vulncheck.com/advisories/fastchat-unauthenticated-worker-registration-ssrf-and-model-spoofing
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