CVE-2026-13434: Improper Input Validation in Red Hat Red Hat OpenShift Virtualization 4
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).
AI Analysis
Technical Summary
The vulnerability arises from KubeVirt's network annotation generator writing the supplied networkName value directly into the launcher pod's v1.multus-cni.io/default-network annotation without enforcing DNS-1123 format validation, JSON detection, or special character rejection. The only check rejects empty strings. When the ExternalNetResourceInjection Beta feature gate is enabled (introduced in KubeVirt v1.8.0, shipped in OpenShift Virtualization 4.21), the normal NetworkAttachmentDefinition (NAD) lookup that would catch malformed names is skipped. This allows a tenant with kubevirt.io:edit permissions to inject a JSON-formatted NetworkSelectionElement array specifying arbitrary namespaces, NAD names, static IPs, and MAC addresses. Multus on the node parses this JSON and attaches the launcher pod to specified network attachments in any namespace, enabling cross-namespace network access and IP/MAC impersonation on network segments normally segregated from tenant workloads.
Potential Impact
The vulnerability allows a tenant with kubevirt.io:edit permissions to bypass network segmentation controls by injecting arbitrary network attachment configurations across namespaces. This can lead to cross-namespace network access and IP/MAC address impersonation on network segments that are normally isolated, potentially compromising network security boundaries within the cluster. The impact is limited by the requirement that the ExternalNetResourceInjection feature gate be enabled (off by default) and that the attacker have edit permissions on the kubevirt.io resource.
Mitigation Recommendations
Patch status is not yet confirmed — check the Red Hat advisory at https://access.redhat.com/security/cve/CVE-2026-13434 for current remediation guidance. Until a patch is available, ensure that the ExternalNetResourceInjection Beta feature gate remains disabled unless explicitly required and that tenant permissions are tightly controlled to prevent unauthorized kubevirt.io:edit access. Disabling the feature gate prevents the bypass of NAD lookup validation, mitigating the vulnerability.
CVE-2026-13434: Improper Input Validation in Red Hat Red Hat OpenShift Virtualization 4
Description
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).
CVSS v3.1
Score 4.9medium
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability arises from KubeVirt's network annotation generator writing the supplied networkName value directly into the launcher pod's v1.multus-cni.io/default-network annotation without enforcing DNS-1123 format validation, JSON detection, or special character rejection. The only check rejects empty strings. When the ExternalNetResourceInjection Beta feature gate is enabled (introduced in KubeVirt v1.8.0, shipped in OpenShift Virtualization 4.21), the normal NetworkAttachmentDefinition (NAD) lookup that would catch malformed names is skipped. This allows a tenant with kubevirt.io:edit permissions to inject a JSON-formatted NetworkSelectionElement array specifying arbitrary namespaces, NAD names, static IPs, and MAC addresses. Multus on the node parses this JSON and attaches the launcher pod to specified network attachments in any namespace, enabling cross-namespace network access and IP/MAC impersonation on network segments normally segregated from tenant workloads.
Potential Impact
The vulnerability allows a tenant with kubevirt.io:edit permissions to bypass network segmentation controls by injecting arbitrary network attachment configurations across namespaces. This can lead to cross-namespace network access and IP/MAC address impersonation on network segments that are normally isolated, potentially compromising network security boundaries within the cluster. The impact is limited by the requirement that the ExternalNetResourceInjection feature gate be enabled (off by default) and that the attacker have edit permissions on the kubevirt.io resource.
Mitigation Recommendations
Patch status is not yet confirmed — check the Red Hat advisory at https://access.redhat.com/security/cve/CVE-2026-13434 for current remediation guidance. Until a patch is available, ensure that the ExternalNetResourceInjection Beta feature gate remains disabled unless explicitly required and that tenant permissions are tightly controlled to prevent unauthorized kubevirt.io:edit access. Disabling the feature gate prevents the bypass of NAD lookup validation, mitigating the vulnerability.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- redhat
- Date Reserved
- 2026-06-26T14:59:17.292Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
- Vendor Advisory Urls
- [{"url":"https://access.redhat.com/security/cve/CVE-2026-13434","vendor":"Red Hat"}]
Threat ID: 6a3eae476e08203f7dc7e0c0
Added to database: 06/26/2026, 16:52:23 UTC
Last enriched: 07/03/2026, 22:34:53 UTC
Last updated: 08/09/2026, 12:41:08 UTC
Views: 56
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