# CVE-2026-74721: accel/amxdna: Fix page-insertion errors in amdxdna_insert_pages()

> A use-after-free vulnerability in the Linux kernel's AMD XDNA driver allows local attackers to cause reference count underflows, potentially leading to privilege escalation or system crashes.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 22 Aug 2026
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2026-74721, DEBIAN-CVE-2026-74721, GHSA-grmx-x9wr-gmvh, UBUNTU-CVE-2026-74721

## What is CVE-2026-74721?

CVE-2026-74721 is a high-severity use after free vulnerability in Linux, published on 22 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:

accel/amxdna: Fix page-insertion errors in amdxdna_insert_pages()

Two error paths in amdxdna_insert_pages() called vma->vm_ops->close(vma)
before returning an error code to the caller.  This is incorrect:
amdxdna_gem_obj_mmap() registers an HMM interval notifier before calling
amdxdna_insert_pages(), and on a hard error it jumps to hmm_unreg to undo
that registration.  Calling vm_ops->close() manually — which drops the
shmem pages_pin_count and the GEM object reference that backs the VMA —
before the mmap syscall has even returned causes those resources to be
released while the VMA is still alive.  The kernel VMA teardown will call
vm_ops->close() a second time when the process later unmaps the range,
producing a reference count underflow.

Replace both hard-error returns with a deferred-fault approach that keeps
the VMA alive and retries page insertion through the HMM range-fault path.

## Which versions are affected by CVE-2026-74721?


## How do I fix CVE-2026-74721?

Apply the vendor's patch.

## Is CVE-2026-74721 being exploited?

There is no known exploitation of CVE-2026-74721 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74721 and fix it if it is affected.

What it is: CVE-2026-74721 is a high-severity use after free vulnerability in Linux, published on 22 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-2026-74721 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-2026-74721/ (Markdown: https://insights.sbomify.com/CVE-2026-74721/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74721
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74721
- OSV: https://osv.dev/vulnerability/CVE-2026-74721

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74721/
Summaries are generated and may contain mistakes; the official description above is the record.