CVE-2024-43894 in Linux
Summary
by MITRE • 08/26/2024
In the Linux kernel, the following vulnerability has been resolved:
drm/client: fix null pointer dereference in drm_client_modeset_probe
In drm_client_modeset_probe(), the return value of drm_mode_duplicate() is assigned to modeset->mode, which will lead to a possible NULL pointer dereference on failure of drm_mode_duplicate(). Add a check to avoid npd.
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Analysis
by VulDB Data Team • 09/29/2025
The vulnerability identified as CVE-2024-43894 represents a critical null pointer dereference issue within the Linux kernel's direct rendering manager client subsystem. This flaw exists in the drm_client_modeset_probe function where the return value from drm_mode_duplicate() is directly assigned to modeset->mode without proper validation. When drm_mode_duplicate() fails to duplicate a mode structure, it returns NULL, but the calling code does not verify this condition before proceeding with operations that assume a valid pointer. This oversight creates a potential crash scenario that could be exploited to disrupt system operations or potentially escalate privileges depending on the execution context.
The technical implementation of this vulnerability stems from inadequate error handling practices within the graphics subsystem of the Linux kernel. The drm_client_modeset_probe function is responsible for managing display mode settings in client applications, and during the mode duplication process, it fails to check whether the drm_mode_duplicate() call successfully completed. This specific flaw aligns with CWE-476 which identifies null pointer dereference as a common vulnerability pattern in software development. The absence of proper validation creates a condition where subsequent code execution attempts to access memory through a NULL pointer, leading to system instability and potential denial of service conditions.
The operational impact of this vulnerability extends beyond simple system crashes to potentially affect graphics rendering capabilities across various Linux distributions that utilize the direct rendering manager framework. When exploited, this vulnerability could cause applications relying on DRM client functionality to terminate unexpectedly, resulting in display corruption, application failures, or complete system hang conditions. The vulnerability affects systems using the Linux kernel's graphics subsystem where drm_client_modeset_probe is invoked, particularly impacting desktop environments, virtualization platforms, and embedded systems that depend on proper graphics mode management. Attackers could leverage this weakness to perform denial of service attacks against systems running affected kernel versions, potentially disrupting critical graphics operations in enterprise environments.
Mitigation strategies for CVE-2024-43894 primarily involve applying the patched kernel version that includes the necessary validation check before assigning the return value from drm_mode_duplicate(). The fix implements a straightforward conditional check to verify that the duplicated mode structure is not NULL before proceeding with operations that require a valid pointer. This remediation follows established security practices and aligns with ATT&CK technique T1499.004 which addresses denial of service through resource exhaustion and system instability. System administrators should prioritize updating their kernel installations to versions containing the patch, particularly in production environments where graphics stability is critical. Additionally, monitoring for unusual system crashes or display-related errors can help identify potential exploitation attempts, while implementing proper kernel hardening measures such as stack canaries and address space layout randomization can provide additional defense in depth against potential exploitation scenarios.