CVE-2026-53524: Weechat

Medium severity, CVSS 6.5. EPSS: 0.5% chance of exploitation in the next 30 days.

WeeChat (Wee Enhanced Environment for Chat) is a free chat client. In versions 4.3.0 through 4.9.0, the WeeChat relay module's WebSocket permessage-deflate decompression function relay_websocket_inflate() has no upper bound on output size. An authenticated relay user can send a small compressed WebSocket frame (~100 bytes) that decompresses to gigabytes, exhausting all server memory and crashing the entire WeeChat process. The api protocol enables permessage-deflate and requires authentication before WebSocket upgrade. Version 4.9.1 patches the issue.

Affected products

• Weechat Weechat: from 4.3.0, before 4.9.1 (fixed in 4.9.1)

Published 2026-08-21. Last modified 2026-09-09.