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A vulnerability exists in the KubeVirt guest agent (virt-launcher) where its mechanism for reporting guest information, specifically network interfaces, lacks sufficient validation or rate-limiting. When the guest agent is active inside a Virtual Machine Instance (VMI), a malicious user with access to the guest operating system can manipulate the system to generate and report an artificially high number of virtual network interfaces. This is typically done by creating numerous dummy or virtual network interfaces within the VM’s OS. The guest agent periodically collects this information and sends it to the host-side virt-handler component via the VM’s serial console or a dedicated channel. The host system processes these reports to update the VMI’s status in the Kubernetes API. By flooding the system with a massive volume of interface reports (e.g., thousands), the attacker can exhaust the memory or processing capacity of the virt-handler or overwhelm the update mechanism for the VMI’s configuration. This creates a backlog, effectively blocking the Kubernetes control plane from applying new configuration updates or administrative commands to that specific VMI. The result is a denial-of-service condition for administrative operations, as the cluster administrator loses the ability to modify the VMI’s state (e.g., stop, migrate, or reconfigure it) while the VM itself may continue running normally.
Platform: KubeVirt
Version: v1.3.0
Vulnerability: Guest Agent DoS
Severity: Moderate
date: Jan 26 2026
Prediction: Patch by Feb 2026
What Undercode Say:
!/bin/bash
for i in {1..10000}; do
ip link add dummy$i type dummy
ip link set dummy$i up
done
Floods guest agent report queue
How Exploit:
Malicious VM user executes interface flooding script. Guest agent reports all interfaces. Host-side update channel becomes saturated. New VMI config updates are blocked.
Protection from this CVE
Rate-limit guest agent reports. Validate interface count reasonableness. Update to patched version.
Impact:
Administrative operations DoS. Loss of VM management control. VMI configuration freeze.
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Sources:
Reported By: github.com
Extra Source Hub:
Undercode
