# CVE-2026-64449: staging: vme_user: bound slave read/write to the kern_buf size

> A missing bounds check in the Linux kernel vme_user driver allows out-of-bounds writes, potentially leading to memory corruption and privilege escalation.

- **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:** 25 Jul 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-64449, DEBIAN-CVE-2026-64449, GHSA-fqjm-fj8x-6hp3, ROOT-OS-DEBIAN-12-CVE-2026-64449, ROOT-OS-UBUNTU-2204-CVE-2026-64449, UBUNTU-CVE-2026-64449

## What is CVE-2026-64449?

CVE-2026-64449 is a high-severity memory corruption vulnerability in Linux kernel, published on 25 Jul 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:

staging: vme_user: bound slave read/write to the kern_buf size

The SLAVE-path helpers buffer_to_user() and buffer_from_user() copy
'count' bytes into/out of the fixed-size kern_buf (size_buf ==
PCI_BUF_SIZE == 0x20000, 128 KiB) using *ppos as the offset, without
bounding *ppos + count against size_buf.

vme_user_write()/vme_user_read() only clamp count to the VME window size
(image_size = vme_get_size(resource)), which VME_SET_SLAVE sets from the
user-supplied slave.size -- validated against the VME address space (up
to VME_A32_MAX = 4 GiB), not against PCI_BUF_SIZE.  When the window
exceeds 128 KiB, a write()/read() copies past the kern_buf allocation.

Clamp count against size_buf in both helpers, with an early return when
*ppos is already at/after the buffer end.  *ppos is >= 0 here (the caller
rejects negative offsets), so size_buf - *ppos cannot wrap.  This mirrors
the existing clamp in the MASTER-path helpers resource_to_user() /
resource_from_user(), and matches the read()/write() convention of a
short transfer at end-of-buffer.

Found by static analysis (CodeQL taint tracking + CBMC bounded model
checking) and confirmed dynamically under KASAN with the vme_fake bridge:

  BUG: KASAN: slab-out-of-bounds in _copy_from_user+0x2d/0x80
  Write of size 262144 at addr ffff888004100000 by task trigger/68
    _copy_from_user+0x2d/0x80
    vme_user_write+0x13e/0x240 [vme_user]
    vfs_write+0x1b8/0x7a0
    ksys_write+0xb8/0x150

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-64449?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-64449?

Apply the vendor's patch.

## Is CVE-2026-64449 being exploited?

There is no known exploitation of CVE-2026-64449 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64449 and fix it if it is affected.

What it is: CVE-2026-64449 is a high-severity memory corruption vulnerability in Linux kernel, published on 25 Jul 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-2026-64449 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2026-64449/ (Markdown: https://insights.sbomify.com/CVE-2026-64449/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64449
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64449
- OSV: https://osv.dev/vulnerability/CVE-2026-64449

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64449/
Summaries are generated and may contain mistakes; the official description above is the record.