CVE-2023-53389 in Linux
Summary
by MITRE • 09/18/2025
In the Linux kernel, the following vulnerability has been resolved:
drm/mediatek: dp: Only trigger DRM HPD events if bridge is attached
The MediaTek DisplayPort interface bridge driver starts its interrupts as soon as its probed. However when the interrupts trigger the bridge might not have been attached to a DRM device. As drm_helper_hpd_irq_event() does not check whether the passed in drm_device is valid or not, a NULL pointer passed in results in a kernel NULL pointer dereference in it.
Check whether the bridge is attached and only trigger an HPD event if it is.
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Analysis
by VulDB Data Team • 12/11/2025
The vulnerability identified as CVE-2023-53389 resides within the Linux kernel's MediaTek DisplayPort interface bridge driver component, specifically affecting the drm/mediatek subsystem. This issue represents a classic null pointer dereference scenario that can lead to system instability and potential denial of service conditions. The flaw manifests in the driver's interrupt handling mechanism where the DisplayPort bridge begins processing interrupts immediately upon device probing without proper validation of its attachment state to a DRM device. This premature interrupt processing creates a race condition where interrupt handlers attempt to access DRM device structures that may not yet be properly initialized or could have been detached, leading to kernel space crashes.
The technical implementation of this vulnerability stems from the improper validation within the drm_helper_hpd_irq_event() function which serves as a critical interrupt handler for hotplug detection events. When DisplayPort interrupts are triggered, the system passes a drm_device pointer to this function without verifying whether the pointer references a valid DRM device structure. In scenarios where the bridge has not yet been attached to a DRM device or has been detached, this function receives a NULL pointer which subsequently results in a kernel NULL pointer dereference. This type of vulnerability falls under CWE-476 which specifically addresses null pointer dereference conditions in software implementations, making it a direct security concern for kernel-level stability and system integrity.
The operational impact of this vulnerability extends beyond simple system crashes to potentially compromise the entire display subsystem functionality on affected Linux systems. When the kernel experiences a NULL pointer dereference in kernel space, it typically results in a kernel oops or system crash that can cause complete system lockup or forced reboot. This is particularly concerning for embedded systems, mobile devices, and servers that rely on the MediaTek DisplayPort interface for video output management. The vulnerability affects systems running Linux kernels that include the MediaTek DisplayPort bridge driver code, potentially impacting a wide range of devices including smartphones, tablets, embedded systems, and automotive infotainment systems that utilize MediaTek chipsets. The disruption can occur at any time during system operation when DisplayPort interrupts are generated, making it difficult to predict or prevent.
The mitigation strategy for this vulnerability involves implementing proper validation checks within the interrupt handling code to ensure that the bridge is properly attached to a DRM device before triggering HPD events. The fix requires modifying the driver to check the attachment state of the bridge before invoking the drm_helper_hpd_irq_event() function, thereby preventing the execution path that leads to null pointer dereference. This approach aligns with the principle of defensive programming and follows established best practices for kernel module development. Organizations should prioritize applying the kernel patches that address this specific vulnerability, which typically involve adding conditional checks to verify bridge attachment status before event triggering. The mitigation also aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, as system crashes caused by this vulnerability can effectively deny service to users relying on the display functionality. System administrators should monitor their kernel versions and apply security updates promptly, as this vulnerability represents a critical stability issue that can be exploited to cause persistent system disruptions.