# CVE-2026-62963: Centrifugal Centrifugo denial of service via WebSocket decompression bomb

Source: https://junglewise.ai/threats/cve-2026-62963-centrifugal-centrifugo-denial-of-service-via-websocket  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-16. Updated: 2026-07-16  
License: CC BY 4.0 with a link back

CVE-2026-62963 · Severity: info · CVSS 8.7 · Published 2026-07-16

Centrifugo, a real-time messaging server, is vulnerable to a denial-of-service attack when using compressed WebSocket connections. An attacker can send a specially crafted, highly compressed message (a 'decompression bomb') that consumes excessive memory and CPU when the server attempts to process it. This can lead to server crashes or significant performance degradation, impacting the availability of real-time features for all users.

Technologies: [Centrifugal Centrifugo](https://junglewise.ai/threats/technologies/centrifugo). Vendors: [Centrifugal](https://junglewise.ai/threats/vendors/centrifugal).

## Quick answers

**Is CVE-2026-62963 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-62963 being exploited in the wild.

**How severe is CVE-2026-62963?** Informational severity, with a CVSS score of 8.7, published 16 July 2026.

**Which products and versions are affected?** Centrifugal Centrifugo < 6.8.4.

**Is there a fix for CVE-2026-62963?** A patch was published on 2026-06-28: Fix committed to master branch Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-62963 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-62963?** Check whether you run Centrifugal Centrifugo at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A resource exhaustion vulnerability exists in Centrifugo's unidirectional WebSocket transport when 'uni_websocket.compression' is enabled. While the server enforced 'uni_websocket.message_size_limit' against the compressed wire-frame length, the 'ReadMessage' function used 'io.ReadAll' after decompression without an output cap. This allows an unauthenticated remote attacker to send a 'decompression bomb'—a small compressed payload that expands into a massive amount of data—triggering excessive memory and CPU consumption. The vulnerability is rooted in 'internal/websocket/conn.go' and 'internal/websocket/compression.go'. Version 6.8.4 fixes this by introducing 'decompressed_message_size_limit' to bound the size of messages after decompression.

## Affected products

- Centrifugal Centrifugo < 6.8.4

## Timeline

- 2026-06-28: patched: Fix committed to master branch
- 2026-06-30: advisory: GitHub Security Advisory published
- 2026-07-16: disclosed: CVE published to NVD

## References

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

## Related threats

- [Centrifugo header spoofing via client-controlled emulation](https://junglewise.ai/threats/cve-2026-71485-centrifugo-header-spoofing-via-client-controlled-emulation)
- [Centrifugal Centrifugo authentication bypass in JWKS endpoint verification](https://junglewise.ai/threats/cve-2026-49998-centrifugal-centrifugo-authentication-bypass-in-jwks-endpoint)