CVE-2026-53360

A flaw was found in the Linux kernel's KVM (Kernel-based Virtual Machine) subsystem, specifically within the SEV (Secure Encrypted Virtualization) feature. A malicious guest operating system utilizing SEV-SNP (Secure Nested Paging) can exploit an out-of-bounds write vulnerability due to improper validation of guest-controlled input during Guest-Host Communication Block (GHCB) operations. This allows the guest to read and write beyond allocated memory regions, leading to host kernel heap memory corruption and disclosure of sensitive heap layout information. This could enable a malicious guest to escalate privileges on the host system.

Red Hat Enterprise Linux 6 and 7 are not affected by this flaw, as they did not include support for KVM AMD Secure Encrypted Virtualization (SEV). AMD SEV is currently provided as a Technology Preview in RHEL 8. AMD SEV-SNP (Secure Nested Paging) is currently provided as a Technology Preview in RHEL 9 and 10. Therefore, SEV-SNP is not supported for production use across all versions of Red Hat Enterprise Linux.

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.

If confidential VMs are not in use, this vulnerability can be mitigated by disabling SEV-SNP support on the host, removing the attack surface entirely. Create a file in /etc/modprobe.d/ with a descriptive name, such as cve-2026-53360-mitigation.conf. In that file, disable SEV-SNP for the kvm_amd kernel module:

options kvm_amd sev_snp=0

To validate, read the file /sys/module/kvm_amd/parameters/sev_snp. This file should read N to indicate that the feature is disabled.

If SEV-SNP cannot be disabled, run SEV-SNP hosts on isolated environments and restrict the ability to create SNP-enabled VMs to trusted tenants/administrators only.