CVE-2026-72138 xen/gntdev: fix error handling in ioctl
A local attacker can trigger a memory leak and dangling list entry in the Xen grant device driver, potentially leading to denial of service or 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-2026-72138?
CVE-2026-72138 is a memory corruption 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:
xen/gntdev: fix error handling in ioctl
When gntdev_ioctl_map_grant_ref() fails to copy the operation result back to userspace after successfully adding the mapping to the list, the error path returns -EFAULT without releasing the reference acquired by gntdev_alloc_map(). The mapping remains in priv->maps with a refcount of 1, causing a memory leak and a dangling list entry.
Additionally, gntdev_add_map() may modify map->index to avoid overlap with existing mappings. Therefore, the index returned to userspace must be obtained after gntdev_add_map() completes.
Fix this by holding the mutex across gntdev_add_map(), retrieving the correct index, and copy_to_user(). If copy_to_user() fails, remove the mapping from the list and release the reference while still holding the lock.
Fix these issues by properly handling all error cases.
Which versions are affected by CVE-2026-72138?
How do I fix CVE-2026-72138?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-72138 being exploited?
There is no known exploitation of CVE-2026-72138 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72138, DEBIAN-CVE-2026-72138, GHSA-2fp3-4qp4-w8m7, UBUNTU-CVE-2026-72138.