CVE-2026-74573 iommu/arm-smmu-v3-iommufd: Require exactly one Stream ID for a vDEVICE
A missing check in the Linux kernel's ARM SMMU driver allows out-of-bounds reads or invalidations when devices have zero or multiple streams, potentially causing a crash.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74573?
CVE-2026-74573 is a critical vulnerability in Linux, published on 15 Aug 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/arm-smmu-v3-iommufd: Require exactly one Stream ID for a vDEVICE
arm_vsmmu_vsid_to_sid() maps a guest's vSID to a single physical Stream ID taken from master->streams[0], assuming a device has exactly one stream. A device with several streams gets only its first one mapped, so a guest vSID invalidation cannot reach the others' ATC and IOTLB entries; a device with none makes master->streams a ZERO_SIZE_PTR, read out of bounds.
Add an arm_vsmmu_vdevice_init() op to reject the vDEVICE with -EOPNOTSUPP when master->num_streams is not one, rather than mapping it silently.
Which versions are affected by CVE-2026-74573?
How do I fix CVE-2026-74573?
Apply the vendor's patch.
Is CVE-2026-74573 being exploited?
There is no known exploitation of CVE-2026-74573 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-74573, DEBIAN-CVE-2026-74573, GHSA-p5wj-hqvh-c7x4, UBUNTU-CVE-2026-74573.