CVE-2026-21863
Description
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).
Statement
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.
Mitigation
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.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
An attacker could get secret values such as cryptographic keys, PII, memory addresses, or other information that could be used in additional attacks.
Confidentiality
Technical Impact: Bypass Protection Mechanism
Out-of-bounds memory could contain memory addresses or other information that can be used to bypass ASLR and other protection mechanisms in order to improve the reliability of exploiting a separate weakness for code execution.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
An attacker could cause a segmentation fault or crash by causing memory to be read outside of the bounds of the buffer. This is especially likely when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string.
Other
Technical Impact: Varies by Context
The read operation could produce other undefined or unexpected results.
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