# CVE-2026-31624: HID: core: clamp report_size in s32ton() to avoid undefined shift

> A malicious HID device can trigger an undefined shift in the Linux kernel, potentially causing a 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:** 24 Apr 2026
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-83702, BELL-CVE-2026-31624, DEBIAN-CVE-2026-31624, GHSA-7r46-pv4v-9gxj, ROOT-OS-DEBIAN-11-CVE-2026-31624, ROOT-OS-DEBIAN-12-CVE-2026-31624, ROOT-OS-DEBIAN-13-CVE-2026-31624, ROOT-OS-UBUNTU-2204-CVE-2026-31624, ROOT-OS-UBUNTU-2404-CVE-2026-31624, UBUNTU-CVE-2026-31624

## What is CVE-2026-31624?

CVE-2026-31624 is a medium-severity vulnerability in Linux kernel, published on 24 Apr 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:

HID: core: clamp report_size in s32ton() to avoid undefined shift

s32ton() shifts by n-1 where n is the field's report_size, a value that
comes directly from a HID device.  The HID parser bounds report_size
only to <= 256, so a broken HID device can supply a report descriptor
with a wide field that triggers shift exponents up to 256 on a 32-bit
type when an output report is built via hid_output_field() or
hid_set_field().

Commit ec61b41918587 ("HID: core: fix shift-out-of-bounds in
hid_report_raw_event") added the same n > 32 clamp to the function
snto32(), but s32ton() was never given the same fix as I guess syzbot
hadn't figured out how to fuzz a device the same way.

Fix this up by just clamping the max value of n, just like snto32()
does.

## Which versions are affected by CVE-2026-31624?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31624?

Apply the vendor's patch.

## Is CVE-2026-31624 being exploited?

There is no known exploitation of CVE-2026-31624 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-2026-31624 and fix it if it is affected.

What it is: CVE-2026-31624 is a medium-severity vulnerability in Linux kernel, published on 24 Apr 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-2026-31624 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-2026-31624/ (Markdown: https://insights.sbomify.com/CVE-2026-31624/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31624
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31624
- OSV: https://osv.dev/vulnerability/CVE-2026-31624

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31624/
Summaries are generated and may contain mistakes; the official description above is the record.