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

> Unauthenticated attackers can cause denial of service via decompression bombs in Centrifugo's WebSocket transport when compression is enabled.

- **Severity:** High 8.7 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Jul 2026
- **Updated:** 17 Jul 2026
- **Also known as:** GHSA-q6mr-3g59-5m8x

## What is CVE-2026-62963?

CVE-2026-62963 is a high-severity denial of service vulnerability in centrifugal centrifugo, published on 16 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-409 (Improper Handling of Highly Compressed Data (Data Amplification))

## Which versions are affected by CVE-2026-62963?


## How do I fix CVE-2026-62963?

No fix has been published for CVE-2026-62963 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-62963 being exploited?

There is no known exploitation of CVE-2026-62963 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-62963 and fix it if it is affected.

What it is: CVE-2026-62963 is a high-severity denial of service vulnerability in centrifugal centrifugo, published on 16 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-62963 in the wild and no public exploit code.

Affected product: centrifugal centrifugo. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-62963/ (Markdown: https://insights.sbomify.com/CVE-2026-62963/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-62963
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-62963
- OSV: https://osv.dev/vulnerability/CVE-2026-62963

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-62963/
Summaries are generated and may contain mistakes; the official description above is the record.