CVE-2026-89450 iommu/tegra241-cmdqv: Reject a vSID wider than the SID_MATCH field
A guest VM can bypass IOMMU isolation by providing an oversized virtual Stream ID that aliases to a different device, potentially enabling privilege escalation.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89450?
CVE-2026-89450 is a high-severity vulnerability in Linux, published on 11 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
iommu/tegra241-cmdqv: Reject a vSID wider than the SID_MATCH field
tegra241_vintf_init_vsid() programs the guest-provided vSID into SID_MATCH, whose VIRT_SID field spans bits [20:1] with bit 0 as the match-enable flag. The HW therefore matches only a 20-bit Stream ID.
The bound check rejects only virt_sid > UINT_MAX, which admits a value far wider than the field. The write "virt_sid << 1 | 0x1" then drops every bit above 20: a virt_sid of 0x80000000 lands as SID_MATCH = 0x1, a valid match on vSID 0, so the entry aliases the wrong Stream ID. Because vdev->virt_id is guest-controlled, a VMM can trigger it.
Validate virt_sid against the field width with FIELD_MAX(), and program the register with FIELD_PREP() so the value and the field stay consistent.
Which versions are affected by CVE-2026-89450?
How do I fix CVE-2026-89450?
Apply the vendor's patch.
Is CVE-2026-89450 being exploited?
There is no known exploitation of CVE-2026-89450 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-89450, DEBIAN-CVE-2026-89450, GHSA-4jcm-3g5m-55hr, UBUNTU-CVE-2026-89450.