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.
Published: 2026-09-04
Score: 9.3 Critical
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories

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History

Fri, 04 Sep 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Fri, 04 Sep 2026 16:15:00 +0000

Type Values Removed Values Added
First Time appeared Lm-sys
Lm-sys fastchat
Vendors & Products Lm-sys
Lm-sys fastchat

Fri, 04 Sep 2026 14:45:00 +0000

Type Values Removed Values Added
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.
Title FastChat Unauthenticated Worker Registration SSRF and Model Spoofing
Weaknesses CWE-306
References
Metrics cvssV3_1

{'score': 9.4, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L'}

cvssV4_0

{'score': 9.3, 'vector': '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'}


cve-icon MITRE

Status: PUBLISHED

Assigner: VulnCheck

Published:

Updated: 2026-09-04T15:05:18.305Z

Reserved: 2026-09-04T13:51:51.902Z

Link: CVE-2026-85695

cve-icon Vulnrichment

Updated: 2026-09-04T15:05:08.828Z

cve-icon NVD

Status : Received

Published: 2026-09-04T15:17:47.690

Modified: 2026-09-04T15:17:47.690

Link: CVE-2026-85695

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-04T16:00:05Z

Weaknesses