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CVE Record

CVE-2026-21863: Malformed Valkey Cluster bus message can lead to Remote DoS

Valkey is a distributed key-value database. Prior to versions 9.0.2, 8.1.6, 8.0.7, and 7.2.12, a malicious actor with access to the Valkey clusterbus port can send an invalid packet that may cause an out bound read, which might result in the system crashing. The Valkey clusterbus packet processing code does not validate that a clusterbus ping extension packet is located within buffer of the clusterbus packet before attempting to read it. Versions 9.0.2, 8.1.6, 8.0.7, and 7.2.12 fix the issue. As an additional mitigation, don't expose the cluster bus connection directly to end users, and protect the connection with its own network ACLs.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Valkey clusters running vulnerable versions can be crashed by a malformed message sent to the cluster bus port. This is an availability-only issue: sources do not indicate data theft or modification. Business urgency depends on whether the cluster bus is reachable by untrusted networks or tenants.

Executive priority

Treat as high priority for clustered Valkey systems exposed across broad internal networks, tenant networks, or the internet. Prioritize segmentation immediately and patch during the next urgent maintenance window, because exploitation could disrupt dependent applications without requiring credentials.

Technical view

CVE-2026-21863 is a CWE-125 out-of-bounds read in Valkey cluster bus packet processing. The code may read a ping extension outside the packet buffer when handling an invalid cluster bus message, potentially crashing the process. Affected ranges are Valkey before 7.2.12, 8.0.7, 8.1.6, and 9.0.2.

Likely exposure

Exposure is most likely in self-managed Valkey clusters where the cluster bus port is reachable beyond trusted nodes. Single-node deployments or clusters with strict node-to-node ACLs are lower exposure, but version inventory is still needed. The supplied sources list Valkey only; do not assume Redis or managed services are affected without vendor confirmation.

Exploitation context

The CVSS vector is network, low complexity, no privileges, no user interaction, with high availability impact. The source bundle does not report active exploitation, and KEV is false. Practical risk depends on whether an attacker can reach the cluster bus connection.

Researcher notes

Evidence supports a malformed cluster bus message causing an out-of-bounds read and possible crash. The advisory names fixed upstream versions and a network ACL mitigation. No supplied source confirms exploitation in the wild, weaponized tooling, confidentiality impact, or integrity impact.

Mitigation direction

  • Upgrade Valkey to 9.0.2, 8.1.6, 8.0.7, or 7.2.12 or later.
  • Do not expose the cluster bus directly to end users or untrusted networks.
  • Restrict cluster bus access with dedicated network ACLs between trusted cluster nodes.
  • Check Red Hat advisories for affected packaged versions and applicable errata.
  • Monitor Valkey and distribution vendor guidance for any further remediation notes.

Validation and detection

  • Inventory Valkey deployments and record exact major and patch versions.
  • Identify clusters where the cluster bus port is reachable outside trusted node networks.
  • Review firewall, security group, and ACL rules protecting node-to-node cluster communication.
  • Confirm upgraded packages match vendor-fixed versions or relevant Red Hat errata.
  • Check service restart history for unexplained Valkey crashes indicating availability impact.
Prepared
Confidence
high
Sources
10

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-125: Exact CWE lookup

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description · low confidence lookup

Database behavior lookup

The CVE wording references database injection or access, so collection and exfiltration review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2026-21863 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
9Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6GitHub_M
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-21863Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPvalkey: Valkey: Denial of Service via invalid clusterbus packet
other:Red Hat severity ratingcvssV3_1
  • 2026-02-23T21:03:12.281Z: Reported to Red Hat.
  • 2026-02-23T19:41:28.783Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
valkey-iovalkey< 7.2.12, >= 8.0.0, < 8.0.7, >= 8.1.0, < 8.1.6, >= 9.0.0, < 9.0.2Listed
Weakness

CWE details

CWE-125

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-125 · source CWE mapping

Out-of-bounds Read

Out-of-bounds Read represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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