Paper/Archive/CVE-2026-85695

CVE-2026-85695

lm-sys FastChat — FastChat Unauthenticated Worker Registration SSRF and Model Spoofing

Description · from the CVE record

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

ProductAffectedFixed inSource
FastChat≤ 0.2.36–CNA

Scores by source

VulnCheck (CNA)9.4CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
VulnCheck (CNA)9.3CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N
CISA ADPSSVCExploitation: none · Automatable: yes · Technical impact: total

References

refgithub.com/lm-sys/FastChat/issues/3886refgithub.com/lm-sys/FastChatwriteupgithub.com/lm-sys/FastChat/blob/v0.2.36/fastchat/serve/controller.pywriteupvulncheck.com/advisories/fastchat-unauthenticated-worker-registration-ssrf-and-model-spoofing