CVE-2026-74515
HighCVSS 8.8Exploitation Probability (EPSS)
Low risk3th percentile - higher than 3% of all known CVEs
Summary
In the Linux kernel, in the KVM subsystem for s390 architecture in PCI handling, a vulnerability was found where a request to enable interrupt forwarding is not rejected if it is already enabled for the zPCI device. The MPCIFC instruction does not allow re-registering interrupts without first unregistering. The fix adds a proper check, preventing overwriting and resource leaks when the ioctl is called multiple times for the same device.
Risk Assessment
Lack of rejection may lead to overwriting existing interrupt configurations and kernel resource leaks, which could be exploited to destabilize the system or cause a DoS attack.
Recommendation
Apply a Linux kernel update containing the fix for CVE-2026-74515. If not possible, restrict access to the KVM interface for untrusted users.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: KVM: s390: pci: Reject adapter interrupt forwarding if already enabled The MPCIFC instruction doesn't allow registering adapter interrupts without first unregistering. So reject any request to enable interrupt forwarding if its already enabled for the zPCI device. This also fixes overwriting and thus leaking resources when the ioctl is called multiple times for the same device.