Description
A vulnerability was detected in lm-sys fastchat up to 0.2.36. Impacted is the function add_text of the component Arena Side-by-Side View Handler. The manipulation results in incorrect control flow. The attack can be launched remotely. The exploit is now public and may be used. The root cause was fixed in commit 34eca62 for gradio_block_arena_named.py, but three other files were missed.
Problem types
Product status
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
Timeline
| 2026-04-19: | Advisory disclosed |
| 2026-04-19: | VulDB entry created |
| 2026-04-19: | VulDB entry last update |
Credits
Eric-f (VulDB User)
References
vuldb.com/vuln/358243 (VDB-358243 | lm-sys fastchat Arena Side-by-Side View add_text control flow)
vuldb.com/vuln/358243/cti (VDB-358243 | CTI Indicators (IOB, IOC, IOA))
vuldb.com/submit/792228 (Submit #792228 | LM-Sys FastChat <= 0.2.36 Content Moderation Bypass (CWE-670))
github.com/lm-sys/FastChat/issues/3834
gist.github.com/YLChen-007/e45039d23e698222d887ee09735d9d36
github.com/lm-sys/FastChat/