Medium [CVE-2026-13434] Multus default-network annotation injection via unvalidated tenant networkName when ExternalNetResourceInjection is enabled
This medium-severity Red Hat Linux advisory covers CVE-2026-13434 affecting Red Hat OpenShift Virtualization 4.
Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.
VulniPulse record published Record updated
Summary
A flaw was found in KubeVirt's network annotation generator. When a tenant creates a VirtualMachineInstance with a Multus network configuration, the supplied networkName value is written verbatim into the launcher pod's v1.multus-cni.io/default-network annotation without format validation or sanitization.
The only admission check rejects empty strings; no DNS-1123 format validation, JSON detection, or special character rejection is performed. When the ExternalNetResourceInjection Beta feature gate is enabled (off by default, cluster-admin only), the NAD lookup that would otherwise catch malformed names is skipped by design.
A tenant with kubevirt.io:edit permissions can inject a JSON-formatted NetworkSelectionElement array specifying an arbitrary namespace, NAD name, static IP address, and MAC address.
Multus on the node parses this JSON and attaches the launcher pod to the specified network attachment in any namespace, enabling cross-namespace network access and IP/MAC impersonation on network segments normally segregated from tenant workloads.
The ExternalNetResourceInjection feature gate was introduced in KubeVirt v1.8.0 (first shipped in OpenShift Virtualization 4.21). Red Hat has assessed this flaw as Moderate impact for OpenShift Virtualization.
Affected product named by the advisory: Red Hat OpenShift Virtualization 4.
Is CVE-2026-13434 exploited?
No exploitation is reported in the sources VulniPulse tracks: CVE-2026-13434 is not in the CISA KEV catalog (checked ) and this advisory does not report exploitation. That is not proof the vulnerability cannot be exploited.
How do I fix CVE-2026-13434?
The advisory VulniPulse tracks names no fixed release. Follow Red Hat's guidance for workarounds and updates.
Confirm against the vendor advisory before you patch.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative. Check it before change work.
Official advisory · high-confidence parse· fetched 13 days ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists. Confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 13 days ago·verify at source
Mitigation checklist
- If the ExternalNetResourceInjection feature gate has been enabled, disable it by removing it from the HyperConverged CR's spec.featureGates configuration. This restores the NAD lookup that blocks malformed network names. If the feature gate is required for operational reasons, restrict kubevirt.io:edit permissions to trusted users only and enforce NetworkPolicy on sensitive network segments to limit lateral movement from unauthorized attachments.
Official advisory · high-confidence parse· fetched 13 days ago·verify at source
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