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

What is CVE-2025-21963?

CVE-2025-21963 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 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.

Weakness: CWE-190

Which versions are affected by CVE-2025-21963?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2025-21963?

Apply the vendor's patch.

Is CVE-2025-21963 being exploited?

There is no known exploitation of CVE-2025-21963 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as AZL-60282, AZL-60316, BELL-CVE-2025-21963, DEBIAN-CVE-2025-21963, GHSA-h9h6-5fw6-j683, ROOT-OS-UBUNTU-2404-CVE-2025-21963 and 1 more.