CVE-2026-72290

A flaw was found in the Linux kernel's Kernel-based Virtual Machine (KVM) for s390 PCI. During the setup of guest interrupt forwarding, a reference count (refcount) to the Guest Interrupt Service Call (GISC) may not be properly released if subsequent setup steps fail. This resource leak can lead to resource exhaustion, potentially allowing a local attacker to cause a Denial of Service (DoS) to the virtualized environment.

A low impact flaw was found in the Linux kernel's Kernel-based Virtual Machine (KVM) s390 PCI passthrough support in Red Hat Enterprise Linux and Red Hat In-Vehicle OS. When a guest enables adapter interrupt forwarding (AIF) for an assigned PCI device, the kernel registers the guest interrupt service call (GISC) reference before pinning the guest interrupt forwarding pages and allocating the AISB bit. If one of these later setup steps fails, the error unwind path releases the pinned pages and other local state but does not unregister the GISC reference. Repeated failed AIF enable attempts can therefore leak GISC references and progressively exhaust the resources used for guest interrupt forwarding, allowing a local attacker to cause a denial of service against the virtualized environment. There is no impact on confidentiality or integrity. Although the CVSS:3.1 base score is 5.5 (Moderate), Red Hat rates the impact of this flaw as Low because reliably triggering the vulnerable path requires privileged, host-side control of KVM virtual machine setup and s390 PCI passthrough configuration. The kernel and kernel-rt packages in the affected Red Hat Enterprise Linux 8, 9, and 10 streams and Red Hat In-Vehicle OS 2 streams are affected; the fix is deferred to a future scheduled update because the flaw is a low-severity local denial of service, and the residual risk of deferral is limited to resource exhaustion affecting only the availability of s390 KVM virtualization. Red Hat Enterprise Linux 6 ELS, 7 ELS, and the 8.4 and 8.6 z-streams are not affected because the vulnerable code is not present in those releases.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.