EUVD-2026-39599
GHSA-6f2p-2qg2-qqch
Severity by source
AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:L
Raising A to H because OOM-killing virt-handler disrupts all VMs on the node, not just one; all other metrics align with vendor vector.
Primary rating from Vendor (redhat).
CVSS VectorVendor: redhat
Lifecycle Timeline
1DescriptionCVE.org
A flaw was found in KubeVirt's downward metrics virtio-serial server. The server reads guest requests using textproto.Reader.ReadLine(), which buffers input indefinitely until a newline character is received, with no length limit or read deadline. A user with access to a VM guest that has the downward metrics virtio-serial device configured can write a continuous byte stream to the device, causing unbounded memory allocation in the virt-handler process until it is OOM-killed.
AnalysisAI
Unbounded memory allocation in KubeVirt's downward metrics virtio-serial server within Red Hat OpenShift Virtualization 4 allows a local VM guest user to exhaust host-side memory. The virt-handler process - which runs on the Kubernetes node and manages VM lifecycle - uses textproto.Reader.ReadLine() with no read deadline or buffer cap, so a continuous byte stream from the guest causes virt-handler to allocate memory without bound until the Linux OOM killer terminates it. No active exploitation has been confirmed (not in CISA KEV) and no public exploit code has been identified at time of analysis; the CVSS score of 3.8 reflects low severity but the scope-change flag (S:C) correctly captures that the disruption crosses the guest boundary to a privileged host process.
Technical ContextAI
KubeVirt exposes a 'downward metrics' feature through a virtio-serial character device, allowing guest workloads to query hypervisor-side metrics. The host-side server component (running within the virt-handler daemonset pod on the Kubernetes node) accepts guest input via Go's textproto.Reader.ReadLine(), which accumulates bytes in an internal buffer until a newline character 0x0A is received. The library imposes no maximum read size and the server sets no net.Conn read deadline, violating the resource-bounding principle described in CWE-770 (Allocation of Resources Without Limits or Throttling). Because virt-handler runs as a privileged host process managing all VMs on a node, its memory consumption is constrained only by the node's cgroup limits and available RAM. CPE data identifies the affected product as cpe:2.3:a:red_hat:red_hat_openshift_virtualization_4:*:*:*:*:*:*:*:* with no version upper bound disclosed, meaning all current OpenShift Virtualization 4.x releases are presumed affected until Red Hat publishes a fixed version.
RemediationAI
Patch available per vendor advisory - consult https://access.redhat.com/security/cve/CVE-2026-13322 for the released fix version, as no specific patched release number was confirmed in the available source data at time of analysis. Until the patch is applied, the primary compensating control is to disable or remove the downward metrics virtio-serial device from VM configurations where it is not required - this eliminates the attack surface entirely but removes guest-side metrics visibility, which may affect monitoring workflows. A secondary control is to restrict which users or service accounts have console or serial device access inside affected VMs via OpenShift RBAC and KubeVirt VirtualMachine access policies, limiting the pool of principals who can send data to the virtio-serial endpoint. Node-level memory limits on the virt-handler container via Kubernetes resource requests/limits can reduce the blast radius - capping virt-handler memory means the OOM kill occurs sooner and at a predictable threshold, though it does not prevent the denial-of-service itself. Upgrade OpenShift Virtualization to the patched version as the definitive fix once released.
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Same technique Denial Of Service
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