CVE-2025-21964 is an integer overflow vulnerability in the CIFS kernel module of Red Hat Enterprise Linux 9. This flaw occurs during the processing of the acregmax mount option, potentially leading to incorrect behavior in the kernel. Red Hat Product Security has issued an advisory (RHSA-2025:8142) describing the fix and recommending an update. The update addresses the integer overflow to prevent potential security issues related to this flaw. The advisory covers multiple Red Hat Enterprise Linux 9 variants and architectures, including x86_64, s390x, ppc64le, and aarch64. The update requires a system reboot to take effect. No CVSS score is provided, and no exploits are known to be active in the wild.

The integer overflow vulnerability in the CIFS kernel module could lead to unexpected kernel behavior or potential security issues when processing the acregmax mount option. The advisory rates the impact as moderate. There are no reports of active exploitation in the wild. The vulnerability affects the core Linux kernel component, which is critical to system operation.

Red Hat has released an official security update for Red Hat Enterprise Linux 9 that fixes this vulnerability. Users should apply the update as described in the Red Hat advisory RHSA-2025:8142 and reboot their systems to ensure the fix takes effect. No additional mitigations are indicated by the vendor.