# CVE-2026-21863: Valkey Denial of Service via invalid clusterbus packet

Source: https://junglewise.ai/threats/cve-2026-21863-valkey-denial-of-service-via-invalid-clusterbus-packet  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-02-23. Updated: 2026-06-30  
License: CC BY 4.0 with a link back

CVE-2026-21863 · Severity: high · CVSS 7.5 · Published 2026-02-23

Valkey is a high-performance database used for storing and managing data in memory. A vulnerability has been identified where a malicious user with access to the database's internal communication port can send a specially crafted message that causes the system to crash. This could lead to a service outage, disrupting applications that rely on the database for real-time data.

## Quick answers

**Is CVE-2026-21863 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-21863 being exploited in the wild.

**How severe is CVE-2026-21863?** High severity, with a CVSS score of 7.5, published 23 February 2026.

**Which products and versions are affected?** Valkey-io Valkey < 7.2.12, 8.0.0 to < 8.0.7, 8.1.0 to < 8.1.6, 9.0.0 to < 9.0.2; Red Hat Enterprise Linux 9, 10.

**Is there a fix for CVE-2026-21863?** A patch was published on 2026-02-26: Red Hat released security updates for RHEL 10 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-21863 attacked?** It is attacked over the network or from the adjacent network, in a software library.

**Am I affected by CVE-2026-21863?** Check whether anything you run is named in the advisory. 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

An out-of-bounds read vulnerability exists in the Valkey clusterbus packet processing code. The flaw is caused by a failure to validate that a clusterbus ping extension packet is located within the allocated buffer before attempting to read it. An attacker with network access to the clusterbus port can exploit this by sending a malformed packet, leading to a process crash (Denial of Service). The issue is fixed in Valkey versions 9.0.2, 8.1.6, 8.0.7, and 7.2.12. Red Hat has also released updates for affected Enterprise Linux distributions. As a mitigation, administrators should restrict access to the cluster bus port using network ACLs.

## Affected products

- Valkey-io Valkey < 7.2.12, 8.0.0 to < 8.0.7, 8.1.0 to < 8.1.6, 9.0.0 to < 9.0.2
- Red Hat Enterprise Linux 9, 10

## Timeline

- 2026-02-23: disclosed: Initial advisory published by Valkey-io
- 2026-02-23: advisory: CVE-2026-21863 assigned
- 2026-02-26: patched: Red Hat released security updates for RHEL 10
- 2026-03-02: patched: Red Hat released security updates for RHEL 9

## References

- [https://github.com/valkey-io/valkey/security/advisories/GHSA-c677-q3wr-gggq](https://github.com/valkey-io/valkey/security/advisories/GHSA-c677-q3wr-gggq)
- [https://access.redhat.com/errata/RHSA-2026:3443](https://access.redhat.com/errata/RHSA-2026:3443)
- [https://access.redhat.com/errata/RHSA-2026:3507](https://access.redhat.com/errata/RHSA-2026:3507)
- [https://access.redhat.com/errata/RHSA-2026:5445](https://access.redhat.com/errata/RHSA-2026:5445)
- [https://access.redhat.com/errata/RHSA-2026:8753](https://access.redhat.com/errata/RHSA-2026:8753)
- [https://access.redhat.com/security/cve/CVE-2026-21863](https://access.redhat.com/security/cve/CVE-2026-21863)
- [https://bugzilla.redhat.com/show_bug.cgi?id=2442026](https://bugzilla.redhat.com/show_bug.cgi?id=2442026)