TI-2026-05794 Aliases CVE-2026-6607 GHSA-5h65-jx66-j7p5

lm-sys fastchat Worker API Endpoint api_generate resource consumption

HIGH 70CWE-400Published 2026-04-20 · Updated 2026-04-20

Key facts

Attack vector: Network
Privileges required: None
User interaction: None
Attack complexity: Low
Attack requirements: None
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · Low
Fix status: No fix listed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-400.

Summary

A security vulnerability has been detected in lm-sys fastchat up to 0.2.36. This issue affects the function api_generate of the component Worker API Endpoint. The manipulation leads to resource consumption. The attack can be initiated remotely. The exploit has been disclosed publicly and may be used. The identifier of the patch is c9e84b89c91d45191dc24466888de526fa04cf33. It is suggested to install a patch to address this issue. Commit ff66426 patched this issue in api_generate of base_model_worker.py and did miss other entry points.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.00623 50th percentileScored 2026-11-07

Public exploit Yes 1 exploit referenceTagged by the CNA

Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: Yes
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
lm-sys	fastchat	0.2.0; 0.2.1; 0.2.2; 0.2.3; 0.2.4; 0.2.5; 0.2.6; 0.2.7; 0.2.8; 0.2.9; 0.2.10; 0.2.11; 0.2.12; 0.2.13; 0.2.14; 0.2.15; 0.2.16; 0.2.17; 0.2.18; 0.2.19; 0.2.20; 0.2.21; 0.2.22; 0.2.23; 0.2.24; 0.2.25; 0.2.26; 0.2.27; 0.2.28; 0.2.29; 0.2.30; 0.2.31; 0.2.32; 0.2.33; 0.2.34; 0.2.35; 0.2.36	—	No fix listed	CNA
—	fschat (PyPI)	up to 0.2.26	—	No fix listed	GHSA-5h65-jx66-j7p5

fastchat Vendorlm-sys Affected 0.2.0; 0.2.1; 0.2.2; 0.2.3; 0.2.4; 0.2.5; 0.2.6; 0.2.7; 0.2.8; 0.2.9; 0.2.10; 0.2.11; 0.2.12; 0.2.13; 0.2.14; 0.2.15; 0.2.16; 0.2.17; 0.2.18; 0.2.19; 0.2.20; 0.2.21; 0.2.22; 0.2.23; 0.2.24; 0.2.25; 0.2.26; 0.2.27; 0.2.28; 0.2.29; 0.2.30; 0.2.31; 0.2.32; 0.2.33; 0.2.34; 0.2.35; 0.2.36 Fixed in — No fix listed CNA
fschat (PyPI) Vendor— Affected up to 0.2.26 Fixed in — No fix listed GHSA-5h65-jx66-j7p5

CPE names CNA · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:lm-sys:fastchat::::::::	—	—	lm-sys

cpe:2.3:a:lm-sys:fastchat:*:*:*:*:*:*:*:* Versions — — ·lm-sys

Remediation

No fixed version listed by the sources yet.

Timeline

2026-10-02 Threatist record created from CVE-2026-6607
2026-10-03 Alias added: GHSA-5h65-jx66-j7p5
2026-10-25 EPSS moved to the below the 50th percentile
2026-11-05 EPSS moved to the 50th–90th percentile

References

Exploit 1

https://gist.github.com/YLChen-007/87216a2d97a882d619e11dc67cd473b5

Patch 2

Advisory 1

https://nvd.nist.gov/vuln/detail/CVE-2026-6607

Other 3

TI-2024-09320 SSRF in POST /worker_generate_stream API endpoint in lm-sys/fastchat CVSS 3.0CRITICAL 9.3
TI-2024-11482 Server Side Request Forgery in lm-sys/fastchat CVSS 3.0HIGH 7.5
TI-2024-10750 Server-Side Request Forgery in lm-sys/fastchat CVSS 3.0HIGH 7.5
TI-2024-10115 Denial of Service in lm-sys/fastchat CVSS 3.0HIGH 7.5
TI-2024-10111 Denial of Service (DoS) via Multipart Boundary in lm-sys/fastchat CVSS 3.0HIGH 7.5
TI-2026-05795 lm-sys fastchat Arena Side-by-Side View add_text control flow CVSS 4.0MEDIUM 6.9

See all 9 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences