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Vulnerability · Published Aug 21, 2026 · Assigned by GitHub_M

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

Medium 6.5

In plain English

A medium-severity security flaw in weechat from weechat. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 42% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)6.5Medium
Exploit odds (30 days)0.5%top 58.1% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12weechatno fix listedDEBIAN-CVE-2026-53524
Debian:13weechatno fix listedDEBIAN-CVE-2026-53524
Debian:14weechat4.9.3-1DEBIAN-CVE-2026-53524
Ubuntu:22.04:LTSweechatno fix listedUBUNTU-CVE-2026-53524
Ubuntu:24.04:LTSweechatno fix listedUBUNTU-CVE-2026-53524
Ubuntu:26.04:LTSweechatno fix listedUBUNTU-CVE-2026-53524

Affected products (as reported)

VendorProductVersions
weechat weechat >= 4.3.0, < 4.9.1

Weakness: CWE-409 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

References