CVE-2026-45894 iommu/vt-d: Clear Present bit before tearing down PASID entry
A race condition in the Linux kernel IOMMU driver can cause hardware faults or unpredictable behavior during PASID entry teardown.
- 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-2026-45894?
CVE-2026-45894 is a high-severity vulnerability in Linux kernel, published on 27 May 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/vt-d: Clear Present bit before tearing down PASID entry
The Intel VT-d Scalable Mode PASID table entry consists of 512 bits (64 bytes). When tearing down an entry, the current implementation zeros the entire 64-byte structure immediately using multiple 64-bit writes.
Since the IOMMU hardware may fetch these 64 bytes using multiple internal transactions (e.g., four 128-bit bursts), updating or zeroing the entire entry while it is active (P=1) risks a "torn" read. If a hardware fetch occurs simultaneously with the CPU zeroing the entry, the hardware could observe an inconsistent state, leading to unpredictable behavior or spurious faults.
Follow the "Guidance to Software for Invalidations" in the VT-d spec (Section 6.5.3.3) by implementing the recommended ownership handshake:
1. Clear only the 'Present' (P) bit of the PASID entry. 2. Use a dma_wmb() to ensure the cleared bit is visible to hardware before proceeding. 3. Execute the required invalidation sequence (PASID cache, IOTLB, and Device-TLB flush) to ensure the hardware has released all cached references. 4. Only after the flushes are complete, zero out the remaining fields of the PASID entry.
Also, add a dma_wmb() in pasid_set_present() to ensure that all other fields of the PASID entry are visible to the hardware before the Present bit is set.
Weakness: CWE-362
Which versions are affected by CVE-2026-45894?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-45894?
Apply the vendor's patch.
Is CVE-2026-45894 being exploited?
There is no known exploitation of CVE-2026-45894 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-88701, BELL-CVE-2026-45894, DEBIAN-CVE-2026-45894, GHSA-8pm8-q9qq-gqgp, ROOT-OS-DEBIAN-11-CVE-2026-45894, ROOT-OS-DEBIAN-12-CVE-2026-45894 and 3 more.