CVE-2026-31735 iommupt: Fix short gather if the unmap goes into a large mapping
A logic error in the Linux kernel IOMMU unmap path could cause incomplete TLB invalidation, though it is likely not triggerable in practice.
- 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-2026-31735?
CVE-2026-31735 is a high-severity vulnerability in Linux kernel, published on 1 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:
iommupt: Fix short gather if the unmap goes into a large mapping
unmap has the odd behavior that it can unmap more than requested if the ending point lands within the middle of a large or contiguous IOPTE.
In this case the gather should flush everything unmapped which can be larger than what was requested to be unmapped. The gather was only flushing the range requested to be unmapped, not extending to the extra range, resulting in a short invalidation if the caller hits this special condition.
This was found by the new invalidation/gather test I am adding in preparation for ARMv8. Claude deduced the root cause.
As far as I remember nothing relies on unmapping a large entry, so this is likely not a triggerable bug.
Which versions are affected by CVE-2026-31735?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-31735?
Apply the vendor's patch.
Is CVE-2026-31735 being exploited?
There is no known exploitation of CVE-2026-31735 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2026-31735, GHSA-3h92-2gxm-w9x7, UBUNTU-CVE-2026-31735.