# CVE-2025-21962: cifs: Fix integer overflow while processing closetimeo mount option

> An integer overflow in the Linux kernel CIFS module during mount option processing can lead to 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:** 1 Apr 2025
- **Updated:** 23 May 2026
- **Also known as:** AZL-60288, AZL-60334, BELL-CVE-2025-21962, DEBIAN-CVE-2025-21962, GHSA-mg5c-fjcx-j5g5, ROOT-OS-UBUNTU-2404-CVE-2025-21962, UBUNTU-CVE-2025-21962

## What is CVE-2025-21962?

CVE-2025-21962 is a medium-severity vulnerability in Linux kernel, published on 1 Apr 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:

cifs: Fix integer overflow while processing closetimeo mount option

User-provided mount parameter closetimeo of type u32 is intended to have
an upper limit, but before it is validated, the value is converted from
seconds to jiffies which can lead to an integer overflow.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2025-21962?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-21962?

Apply the vendor's patch.

## Is CVE-2025-21962 being exploited?

There is no known exploitation of CVE-2025-21962 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-2025-21962 and fix it if it is affected.

What it is: CVE-2025-21962 is a medium-severity vulnerability in Linux kernel, published on 1 Apr 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-2025-21962 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-2025-21962/ (Markdown: https://insights.sbomify.com/CVE-2025-21962/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21962
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21962
- OSV: https://osv.dev/vulnerability/CVE-2025-21962

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21962/
Summaries are generated and may contain mistakes; the official description above is the record.