CVE-2026-89450

The Linux kernel's tegra241-cmdqv driver (SMMUv3 command-queue virtualization for NVIDIA Tegra241/Grace SoCs) fails to properly validate a guest-provided virtual Stream ID (vSID) before writing it into the SID_MATCH register. The hardware's VIRT_SID field is only 20 bits wide, but the code only rejected values above UINT_MAX, so a wider guest-supplied value could be programmed beyond the field's bounds. Because the vSID/virt_id is guest-controlled, a malicious or compromised virtual machine on an affected host could trigger the bad register write, with high impact to confidentiality, integrity, and availability (CVSS 8.8, effectively a guest-to-host escape primitive). Only systems on Tegra241 (NVIDIA Grace) hardware exposing the virtualized SMMU command queues to guests are affected. No public proof of concept or in-the-wild exploitation is known.

What to do: Apply kernel updates containing the tegra241-cmdqv fix, which validates virt_sid against the 20-bit VIRT_SID field width with FIELD_MAX() and programs the register with FIELD_PREP(). Until patched, restrict or disable assignment of the virtualized SMMU (vcmdq/vSMMU) to untrusted guests on Grace-based hosts. Audit hypervisor logs for guests attempting to configure unusually large Stream ID values on vINTF/vSID setup.