CVE-2026-21863

A flaw was found in Valkey, a distributed key-value database. A malicious actor with access to the Valkey clusterbus port can exploit an input validation vulnerability by sending a specially crafted invalid clusterbus packet. This lack of validation for clusterbus ping extension packets can lead to an out-of-bounds read. Consequently, this may cause the system to crash, resulting in a Denial of Service (DoS).

This issue is rated High severity by Red Hat Product Security, because Valkey is commonly deployed as a network-accessible service or embedded within applications that accept remote input over standard network interfaces. In such environments, a remote attacker can trigger the vulnerability by sending specially crafted data to the service. Successful exploitation results in a service crash, leading to a denial-of-service condition. Although no confidentiality or integrity impacts are observed, the ability to repeatedly crash the service over the network justifies a High availability impact rating.

This vulnerability affects Valkey deployments where the cluster bus connection is exposed.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, restrict network access to the Valkey cluster bus port. Configure network access control lists (ACLs) or firewall rules to ensure that only trusted hosts can connect to the cluster bus port. This limits the attack surface by preventing unauthorized actors from sending malicious clusterbus packets.