CVE-2026-85695FastChat Unauthenticated Worker Registration SSRF and Model Spoofing
Updated under an hour ago ()
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It affects lm-sys FastChat. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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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.
- CVSS
- 9.4 CRITICAL (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
- Weakness (CWE)
- CWE-306
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- VulnCheck
- NVD analysis
- Deferred
- Record last updated
- Oct 1, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
lm-sys FastChat lm_sys:fastchat (from the name) | through 0.2.36 | CNA record |
References
- https://github.com/lm-sys/FastChat/issues/3886issue-tracking
- https://github.com/lm-sys/FastChatproduct
- https://github.com/lm-sys/FastChat/blob/v0.2.36/fastchat/serve/controller.pytechnical-description
- https://www.vulncheck.com/advisories/fastchat-unauthenticated-worker-registration-ssrf-and-model-spoofingthird-party-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.