What’s Vulnerable › Vulnerabilities

CVE-2026-53524: WeeChat has a Decompression Bomb in Relay WebSocket (DoS)

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-21 · updated 2026-10-14
• Weakness: CWE-409

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.

Affected products

• weechat: from 4.3.0, < 4.9.1

References

• https://github.com/weechat/weechat/security/advisories/GHSA-v2v4-45wm-5cr3
• https://github.com/weechat/weechat/security/advisories/GHSA-v2v4-45wm-5cr3

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