CVE-2026-53524 WeeChat has a Decompression Bomb in Relay WebSocket (DoS)
An authenticated user can crash WeeChat by sending a small compressed WebSocket frame that decompresses to gigabytes, exhausting memory.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53524?
CVE-2026-53524 is a medium-severity denial of service vulnerability in weechat, published on 21 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
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.
Weakness: CWE-409
Which versions are affected by CVE-2026-53524?
How do I fix CVE-2026-53524?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-53524 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53524 exists.
Sources
Also known as DEBIAN-CVE-2026-53524, GHSA-v2v4-45wm-5cr3, UBUNTU-CVE-2026-53524.