Medium severity · published Aug 21, 2026
CVE-2026-53524
WeeChat has a Decompression Bomb in Relay WebSocket (DoS)
6.5
CVSS
0.5%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 42% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
WE
weechat · weechat
>= 4.3.0, < 4.9.1 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-53524
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-53524
github.com
https://github.com/weechat/weechat/security/advisories/GHSA-v2v4-45wm-5cr3
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