# CVE-2025-37816: mei: vsc: Fix fortify-panic caused by invalid counted_by() use

> A Linux kernel driver bug causes a fortify-panic and system crash when adding CRC to a buffer, leading to denial of service.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/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:** 8 May 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-37816, DEBIAN-CVE-2025-37816, GHSA-4x4p-c635-2m6r, ROOT-OS-UBUNTU-2404-CVE-2025-37816, UBUNTU-CVE-2025-37816

## What is CVE-2025-37816?

CVE-2025-37816 is a medium-severity memory corruption vulnerability in Linux kernel, published on 8 May 2025. 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:

mei: vsc: Fix fortify-panic caused by invalid counted_by() use

gcc 15 honors the __counted_by(len) attribute on vsc_tp_packet.buf[]
and the vsc-tp.c code is using this in a wrong way. len does not contain
the available size in the buffer, it contains the actual packet length
*without* the crc. So as soon as vsc_tp_xfer() tries to add the crc to
buf[] the fortify-panic handler gets triggered:

[   80.842193] memcpy: detected buffer overflow: 4 byte write of buffer size 0
[   80.842243] WARNING: CPU: 4 PID: 272 at lib/string_helpers.c:1032 __fortify_report+0x45/0x50
...
[   80.843175]  __fortify_panic+0x9/0xb
[   80.843186]  vsc_tp_xfer.cold+0x67/0x67 [mei_vsc_hw]
[   80.843210]  ? seqcount_lockdep_reader_access.constprop.0+0x82/0x90
[   80.843229]  ? lockdep_hardirqs_on+0x7c/0x110
[   80.843250]  mei_vsc_hw_start+0x98/0x120 [mei_vsc]
[   80.843270]  mei_reset+0x11d/0x420 [mei]

The easiest fix would be to just drop the counted-by but with the exception
of the ack buffer in vsc_tp_xfer_helper() which only contains enough room
for the packet-header, all other uses of vsc_tp_packet always use a buffer
of VSC_TP_MAX_XFER_SIZE bytes for the packet.

Instead of just dropping the counted-by, split the vsc_tp_packet struct
definition into a header and a full-packet definition and use a fixed
size buf[] in the packet definition, this way fortify-source buffer
overrun checking still works when enabled.

## Which versions are affected by CVE-2025-37816?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-37816?

Apply the vendor's patch.

## Is CVE-2025-37816 being exploited?

There is no known exploitation of CVE-2025-37816 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-2025-37816 and fix it if it is affected.

What it is: CVE-2025-37816 is a medium-severity memory corruption vulnerability in Linux kernel, published on 8 May 2025. 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-2025-37816 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-2025-37816/ (Markdown: https://insights.sbomify.com/CVE-2025-37816/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-37816
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-37816
- OSV: https://osv.dev/vulnerability/CVE-2025-37816

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-37816/
Summaries are generated and may contain mistakes; the official description above is the record.