# CVE-2026-74395: RDMA/mlx5: Fix devx subscribe-event unwind NULL dereference

> A local attacker with low privileges can trigger a NULL pointer dereference in the Linux kernel RDMA subsystem, causing a system crash.

- **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-2026-74395, DEBIAN-CVE-2026-74395, GHSA-x75h-3pjw-vh4q, UBUNTU-CVE-2026-74395

## What is CVE-2026-74395?

CVE-2026-74395 is a 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:

RDMA/mlx5: Fix devx subscribe-event unwind NULL dereference

MLX5_IB_METHOD_DEVX_SUBSCRIBE_EVENT() links event_sub into sub_list
before initializing the fields used by the shared error path.

If eventfd_ctx_fdget() then fails, the unwind path dereferences
event_sub->ev_file in uverbs_uobject_put() and calls
subscribe_event_xa_dealloc() with an unset xa_key_level1.

subscribe_event_xa_alloc() creates the XA entry exactly once for a given
key_level1, on the first occurrence of that key. The unwind path must
therefore call subscribe_event_xa_dealloc() exactly once for it as well.

Enforce that by adding devx_key_in_sub_list() and calling
subscribe_event_xa_dealloc() only when the last matching pending entry is
being cleaned up.

## Which versions are affected by CVE-2026-74395?


## How do I fix CVE-2026-74395?

Apply the vendor's patch.

## Is CVE-2026-74395 being exploited?

There is no known exploitation of CVE-2026-74395 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74395 and fix it if it is affected.

What it is: CVE-2026-74395 is a 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-2026-74395 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-2026-74395/ (Markdown: https://insights.sbomify.com/CVE-2026-74395/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74395
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74395
- OSV: https://osv.dev/vulnerability/CVE-2026-74395

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74395/
Summaries are generated and may contain mistakes; the official description above is the record.