Overview
CVE-2025-40221 describes a potential vulnerability in the Linux kernel’s media subsystem, specifically within the mg4b driver. This flaw involves the possibility of leaking uninitialized stack data to userspace. A fix has been implemented to address this issue by ensuring that the scan structure is properly initialized before use, preventing the leakage of sensitive or unpredictable data.
Technical Details
The vulnerability stems from the fact that the scan structure within the mg4b driver might not be completely initialized before being used. This can result in parts of the structure containing leftover data from the stack. If this uninitialized structure is then exposed to userspace (e.g., through an ioctl or similar interface), it could potentially leak sensitive information or arbitrary data.
The fix involves explicitly zeroing the scan structure before it’s populated with relevant data. This ensures that any unused portions of the structure contain predictable values (zeros), preventing the unintentional disclosure of stack contents.
CVSS Analysis
Currently, no CVSS score is available for CVE-2025-40221. However, while the risk level is classified as N/A, it is important to acknowledge the potential security implications. The absence of a score does not necessarily mean the vulnerability is negligible; it simply indicates that a formal CVSS assessment has not yet been completed. The severity is determined by the specific information leaked and how an attacker might exploit it.
Possible Impact
The potential impact of this vulnerability is primarily information disclosure. While the leaked data may not always be directly exploitable, it could potentially reveal sensitive information about the kernel’s internal state, memory layout, or other processes. This information could then be used to aid in other attacks or escalate privileges. The severity depends on the nature and extent of the data that can be leaked.
Mitigation and Patch Steps
The recommended mitigation is to apply the patch that addresses this vulnerability. This can be achieved by upgrading to a Linux kernel version that includes the fix. The relevant commits are:
- Commit b792eba44494b4e6ab5006013335f9819f303b8b
- Commit b7f82da7f86479cb6479a76ebe213ece7c77398f
- Commit c0d3f6969bb4d72476cfe7ea9263831f1c283704
Users of affected systems are strongly advised to apply the patch as soon as possible to mitigate the risk.
