CVE-2025-38467 in Linux
Summary
by MITRE • 07/25/2025
In the Linux kernel, the following vulnerability has been resolved:
drm/exynos: exynos7_drm_decon: add vblank check in IRQ handling
If there's support for another console device (such as a TTY serial), the kernel occasionally panics during boot. The panic message and a relevant snippet of the call stack is as follows:
Unable to handle kernel NULL pointer dereference at virtual address 000000000000000 Call trace: drm_crtc_handle_vblank+0x10/0x30 (P) decon_irq_handler+0x88/0xb4 [...]
Otherwise, the panics don't happen. This indicates that it's some sort of race condition.
Add a check to validate if the drm device can handle vblanks before calling drm_crtc_handle_vblank() to avoid this.
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Analysis
by VulDB Data Team • 01/04/2026
This vulnerability exists within the Linux kernel's display subsystem, specifically affecting the exynos graphics driver implementation. The issue manifests as a kernel panic during system boot when multiple console devices are present, particularly when a TTY serial console is configured alongside the graphics console. The vulnerability stems from a race condition in the interrupt request handling mechanism where the driver attempts to process vertical blanking interrupts without proper validation of the display device's readiness to handle such events. This flaw represents a classic null pointer dereference scenario that occurs when the kernel tries to access memory through an invalid pointer reference during the vertical blanking interrupt processing.
The technical implementation flaw occurs in the decon_irq_handler function within the exynos7_drm_decon driver module. When the system boots with multiple console devices, the timing of interrupt processing creates a scenario where drm_crtc_handle_vblank() is invoked before the DRM device structure has been fully initialized or properly registered with the vertical blanking subsystem. This race condition allows the kernel to attempt dereferencing a null pointer at virtual address zero, leading to an immediate system crash. The vulnerability is particularly insidious because it only manifests under specific boot conditions involving multiple console devices, making it difficult to reproduce and diagnose in standard testing environments. This type of vulnerability aligns with CWE-476 Null Pointer Dereference and represents a failure in proper device initialization sequencing.
The operational impact of this vulnerability is significant for embedded systems and mobile devices that utilize the exynos SoC architecture, particularly those running Linux distributions with multiple console configurations. System administrators and device manufacturers could experience unexpected boot failures, requiring manual intervention or recovery procedures. The panic occurs during the critical early boot phase, potentially preventing system boot completion entirely and rendering devices unusable until the issue is resolved. This vulnerability affects the reliability and stability of Linux-based embedded systems, particularly in automotive, industrial, and mobile computing environments where uninterrupted operation is critical. The race condition nature means that the vulnerability may not always manifest, creating intermittent failures that are difficult to detect during routine testing and validation processes.
The recommended mitigation strategy involves implementing a simple but crucial validation check before invoking drm_crtc_handle_vblank() in the interrupt handler. This approach aligns with defensive programming practices and follows the principle of validating all inputs and preconditions before making function calls. The fix ensures that the DRM device structure is properly initialized and capable of handling vertical blanking events before attempting to process them, effectively preventing the null pointer dereference. This mitigation approach is consistent with ATT&CK technique T1499.004 for system network configuration modification and represents a proper input validation and error handling mechanism. System administrators should update their kernels to versions containing this fix, particularly in production environments where multiple console devices are configured or where system reliability is paramount. The solution is minimal and surgical, addressing only the specific race condition without disrupting existing functionality or introducing new side effects.