CVE-2025-40221

Vulnerability

Details

The vulnerability resides in the Linux kernel's mg4b media driver for PCI devices. The scan structure used to transfer data to userspace was not initialized before use, potentially leaking uninitialized stack memory to userspace [1]. This is a classic case of an information disclosure flaw where kernel stack data, which may contain sensitive information, could be exposed.

Exploitation

To exploit this vulnerability, an attacker would need local access to the system and the ability to interact with the affected media device (e.g., via the Video4Linux2 interface). No special privileges beyond normal user access to the device are required, as the driver does not properly zero the stack buffer before copying it to userspace. The attack surface is limited to systems with the mg4b hardware present.

Impact

Successful exploitation could allow an attacker to read uninitialized kernel stack memory, potentially revealing sensitive data such as kernel pointers, cryptographic keys, or other process information. This could aid in bypassing security mechanisms like KASLR or facilitate further exploitation.

Mitigation

The fix has been applied in the Linux kernel stable tree [2]. Users are advised to update to a kernel version containing the commit that zeros the scan structure before use. No workaround is available; updating the kernel is the recommended mitigation.