CVE-2026-80551

A flaw was found in the Linux kernel's s390/vfio_ccw component. This vulnerability arises because the system does not ensure that the address in the first Indirect Data Address Word (IDAW) remains constant between reads. An attacker could potentially exploit this to cause the system to operate with an inconsistent set of IDAWs, leading to data integrity issues or system instability.

A flaw of moderate severity was found in the Linux kernel's s390/vfio_ccw subsystem, affecting the kernel and kernel-rt packages in Red Hat Enterprise Linux 9 and Red Hat Enterprise Linux 10, and the kernel packages in Red Hat In-Vehicle OS 2. When processing a channel program that uses indirect data addressing, the vfio_ccw driver reads the first Indirect Data Address Word (IDAW) separately in order to calculate the size of the buffer needed to read the full indirect data address list (IDAL), but it does not verify that the address in the first IDAW is unchanged between reads. A malicious or compromised guest with access to a vfio_ccw passthrough channel device on an IBM s390x system could modify the guest-supplied IDAW list between these reads, causing the host kernel to operate on an inconsistent set of DMA addresses, which can result in data corruption or a denial of service through a host crash. Red Hat Enterprise Linux 6, 7, and 8 are not affected by this flaw. A fix for the affected streams is currently deferred, so residual risk remains for s390x environments that assign vfio_ccw devices to untrusted guests; the deferral reflects the narrow exposure of the issue, which requires guest-level access to a vfio_ccw-mediated device on s390x hardware, and its moderate severity. Red Hat rates this flaw as Moderate severity with a CVSS 3.1 score of 5.5, which differs from the upstream CVEORG rating of 9.3 (Critical) because successful exploitation requires local guest access to a vfio_ccw device on s390x systems rather than unauthenticated access, and the primary consequence is loss of availability.

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.