# CVE-2026-74712: vdpa/mlx5: Fix buffer length in create_direct_keys()

> A buffer overflow in the Linux kernel's mlx5 vdpa driver allows out-of-bounds reads, potentially leading to system crashes or code execution.

- **Severity:** Critical 9.3 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Aug 2026
- **Updated:** 25 Aug 2026
- **Also known as:** BELL-CVE-2026-74712, DEBIAN-CVE-2026-74712, GHSA-8f7v-7fr8-r5c3, UBUNTU-CVE-2026-74712

## What is CVE-2026-74712?

CVE-2026-74712 is a critical memory corruption 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:

vdpa/mlx5: Fix buffer length in create_direct_keys()

We have seen in our CI the following KASAN message:
BUG: KASAN: slab-out-of-bounds in cmd_exec+0x550/0xca0 [mlx5_core]
Read of size 272 at addr 0000000176795020 by task qemu-system-s39/82764
[...]
[<000011388ab3a7a0>] cmd_exec+0x550/0xca0 [mlx5_core]
[<000011388ab3b61c>] mlx5_cmd_exec_cb+0x25c/0x4f0 [mlx5_core]
[<000011388b21e82e>] mlx5_vdpa_exec_async_cmds+0x22e/0x5e0 [mlx5_vdpa]
[<000011388b21fd44>] create_direct_keys+0x954/0xef0 [mlx5_vdpa]
[...]
The buggy address is located 4128 bytes inside of
allocated 4384-byte region [0000000176794000, 0000000176795120)

So in essence we read 16 bytes beyond 4384-byte allocation.
create_direct_keys calculates the pointer and length for in and out
buffers.
The size calculation for in includes the entire structure
size (out + in + mtt[]) but the pointer passed to cmd_exec points only
to the 'in' field, skipping the 'out' field.

This causes mlx5_copy_to_msg() to read beyond the allocated buffer
by sizeof(out) bytes when copying command data.

Properly calculate the input size to match the pointer and allocation size.

## Which versions are affected by CVE-2026-74712?


## How do I fix CVE-2026-74712?

Apply the vendor's patch.

## Is CVE-2026-74712 being exploited?

There is no known exploitation of CVE-2026-74712 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74712 and fix it if it is affected.

What it is: CVE-2026-74712 is a critical memory corruption 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-2026-74712 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-2026-74712/ (Markdown: https://insights.sbomify.com/CVE-2026-74712/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74712
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74712
- OSV: https://osv.dev/vulnerability/CVE-2026-74712

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74712/
Summaries are generated and may contain mistakes; the official description above is the record.