CVE-2025-40316 in Linux
Summary
by MITRE • 12/08/2025
In the Linux kernel, the following vulnerability has been resolved:
drm/mediatek: Fix device use-after-free on unbind
A recent change fixed device reference leaks when looking up drm platform device driver data during bind() but failed to remove a partial fix which had been added by commit 80805b62ea5b ("drm/mediatek: Fix kobject put for component sub-drivers").
This results in a reference imbalance on component bind() failures and on unbind() which could lead to a user-after-free.
Make sure to only drop the references after retrieving the driver data by effectively reverting the previous partial fix.
Note that holding a reference to a device does not prevent its driver data from going away so there is no point in keeping the reference.
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Analysis
by VulDB Data Team • 02/23/2026
The vulnerability CVE-2025-40316 represents a critical use-after-free condition within the Linux kernel's Direct Rendering Manager (DRM) subsystem, specifically affecting the mediatek driver implementation. This issue manifests in the device management layer where improper reference handling during component driver binding and unbinding operations creates a dangerous state that can be exploited by malicious actors. The vulnerability stems from a flawed implementation that failed to properly address reference counting during device lifecycle operations, creating a scenario where device memory could be accessed after it has been freed, leading to potential system instability or privilege escalation.
The technical flaw occurs in the drm/mediatek driver module where the kernel's device management system maintains references to platform devices during binding operations. When the system attempts to look up DRM platform device driver data during bind() operations, a reference leak was initially addressed through a partial fix introduced in commit 80805b62ea5b. However, this partial solution was not completely removed, creating a reference imbalance that persists during both component bind() failures and unbind() operations. The improper reference handling means that while the system maintains references to devices, it fails to properly manage the lifecycle of driver data associated with those devices, leading to scenarios where driver data structures may be freed while still referenced elsewhere in the system.
This vulnerability directly impacts the operational integrity of Linux systems utilizing mediatek graphics hardware, particularly those running kernel versions that include the affected DRM subsystem. The use-after-free condition creates potential attack vectors where malicious code could exploit the reference imbalance to corrupt memory structures, potentially leading to privilege escalation or system crashes. The flaw is particularly dangerous because it operates at the kernel level where memory corruption can result in complete system compromise. According to CWE classification, this vulnerability maps to CWE-416 Use After Free, which specifically addresses the condition where a pointer is used after the memory it points to has been freed. The ATT&CK framework would categorize this under privilege escalation techniques, as memory corruption vulnerabilities often enable attackers to gain elevated system privileges.
The mitigation strategy requires a complete reversal of the partial fix introduced in commit 80805b62ea5b, ensuring that device references are only dropped after successfully retrieving driver data. This approach aligns with proper kernel development practices where reference counting must be carefully managed to prevent race conditions and memory management issues. The fix ensures that references are properly balanced by removing the erroneous reference management logic that was preventing proper cleanup during both successful and failed bind operations. System administrators should prioritize updating to kernel versions that contain this fix, particularly those that properly implement the complete reversal of the partial fix, ensuring that device reference management follows correct kernel memory management principles where holding references to devices does not prevent driver data from being properly cleaned up and freed.