CVE-2024-26938 in Linux
Summary
by MITRE • 05/01/2024
In the Linux kernel, the following vulnerability has been resolved:
drm/i915/bios: Tolerate devdata==NULL in intel_bios_encoder_supports_dp_dual_mode()
If we have no VBT, or the VBT didn't declare the encoder in question, we won't have the 'devdata' for the encoder. Instead of oopsing just bail early.
We won't be able to tell whether the port is DP++ or not, but so be it.
(cherry picked from commit 26410896206342c8a80d2b027923e9ee7d33b733)
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Analysis
by VulDB Data Team • 01/26/2026
The vulnerability identified as CVE-2024-26938 represents a critical stability issue within the Linux kernel's graphics subsystem, specifically affecting the intel i915 driver responsible for handling Intel graphics hardware. This flaw manifests in the drm/i915/bios component where the function intel_bios_encoder_supports_dp_dual_mode() fails to properly handle cases where device data is unavailable. The root cause stems from inadequate null pointer validation when processing Video BIOS Tables (VBT) that contain configuration data for graphics encoders. When the kernel attempts to access device data structures that have not been initialized or are absent from the VBT, the system experiences a kernel oops condition leading to potential system crashes and instability.
The technical implementation of this vulnerability occurs within the graphics driver's firmware table parsing logic where the kernel expects certain device configuration data to be present in the VBT structure. When the VBT either does not exist or lacks the specific encoder information required for dual-mode display port support, the function attempts to dereference a null pointer reference. This scenario typically occurs in systems where the graphics hardware configuration is not properly documented in the firmware tables, or when using custom or modified hardware configurations that do not conform to standard VBT specifications. The vulnerability directly maps to CWE-476 which describes the weakness of null pointer dereference, a fundamental programming error that can lead to system crashes and potentially security exploits.
The operational impact of this vulnerability extends beyond simple system instability to potentially compromise the reliability of graphics subsystems in Linux environments. When a kernel oops occurs due to this flaw, it results in a kernel panic that can cause complete system shutdown or forced reboot, disrupting user sessions and potentially leading to data loss. The affected systems include any Linux distribution running kernel versions that incorporate the vulnerable i915 driver code, particularly those utilizing Intel graphics hardware with dual-mode display port capabilities. This vulnerability affects desktop, laptop, and server systems where Intel graphics are present, making it a widespread concern across various computing environments.
The mitigation strategy for CVE-2024-26938 involves applying the kernel patch that implements proper null pointer checking before attempting to access device data structures. The fix introduced in commit 26410896206342c8a80d2b027923e9ee7d33b733 modifies the intel_bios_encoder_supports_dp_dual_mode() function to gracefully handle cases where devdata is NULL by returning early from the function instead of attempting to dereference the null pointer. This approach aligns with the ATT&CK framework's concept of privilege escalation through kernel exploitation, though this particular vulnerability is more accurately classified as a system stability issue rather than a direct security exploit. Organizations should prioritize updating their kernel versions to include this fix, particularly those running systems with Intel graphics hardware in production environments where system reliability is critical. The patch demonstrates proper defensive programming practices that prevent kernel-level crashes and maintain system stability even when encountering unexpected firmware configurations.