# 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.

- **Severity:** Not scored
- **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:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-72138, DEBIAN-CVE-2026-72138, GHSA-2fp3-4qp4-w8m7, UBUNTU-CVE-2026-72138

## 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.

## Is CVE-2026-72138 being exploited?

There is no known exploitation of CVE-2026-72138 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72138 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-72138 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-72138/ (Markdown: https://insights.sbomify.com/CVE-2026-72138/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72138
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72138
- OSV: https://osv.dev/vulnerability/CVE-2026-72138

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72138/
Summaries are generated and may contain mistakes; the official description above is the record.