CVE-2025-39705 in Linux
Summary
by MITRE • 09/05/2025
In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: fix a Null pointer dereference vulnerability
[Why]
A null pointer dereference vulnerability exists in the AMD display driver's (DC module) cleanup function dc_destruct(). When display control context (dc->ctx) construction fails (due to memory allocation failure), this pointer remains NULL. During subsequent error handling when dc_destruct() is called, there's no NULL check before dereferencing the perf_trace member (dc->ctx->perf_trace), causing a kernel null pointer dereference crash.
[How]
Check if dc->ctx is non-NULL before dereferencing.
(Updated commit text and removed unnecessary error message) (cherry picked from commit 9dd8e2ba268c636c240a918e0a31e6feaee19404)
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Analysis
by VulDB Data Team • 02/09/2026
The vulnerability described in CVE-2025-39705 represents a critical null pointer dereference issue within the AMD display driver component of the Linux kernel. This flaw exists specifically within the drm/amd/display subsystem, where the display core (DC module) handles graphics output management. The vulnerability manifests during the cleanup process of display control contexts through the dc_destruct() function, which is responsible for properly releasing allocated resources when display operations encounter errors or are terminated. The root cause stems from inadequate null pointer validation during error handling procedures, creating a scenario where kernel memory management can fail catastrophically.
The technical implementation of this vulnerability occurs when the display control context construction process fails, typically due to memory allocation failures during system resource exhaustion or insufficient available memory. During such failure conditions, the dc->ctx pointer remains set to NULL while the error handling mechanism attempts to call dc_destruct() to clean up resources. The function fails to perform a null pointer check before accessing the perf_trace member through dc->ctx->perf_trace, resulting in an immediate kernel crash. This type of vulnerability directly maps to CWE-476, which specifically addresses null pointer dereference conditions in software implementations. The flaw demonstrates poor defensive programming practices where assumptions about pointer validity are not properly validated before memory access operations.
The operational impact of this vulnerability extends beyond simple system crashes to potentially enable denial of service conditions that can affect graphics rendering capabilities and overall system stability. When exploited, the null pointer dereference causes immediate kernel panics, forcing system restarts and potentially leading to data loss or service interruptions in graphics-intensive applications. This vulnerability affects systems utilizing AMD graphics hardware through the Linux kernel's display driver stack, particularly impacting desktop environments, server workloads requiring graphical output, and embedded systems with AMD GPU configurations. The vulnerability's exploitation requires only normal system operation conditions, making it particularly concerning as it can occur during routine display operations or system resource contention scenarios.
Mitigation strategies for this vulnerability involve implementing proper null pointer validation checks within the dc_destruct() function before accessing any members of the dc->ctx structure. The fix requires adding a conditional check to verify that dc->ctx is non-NULL before attempting to dereference the perf_trace member. This approach aligns with established security best practices for kernel development and follows the principle of defensive programming as outlined in various security frameworks. System administrators should prioritize applying the patched kernel version that includes the cherry-picked commit 9dd8e2ba268c636c240a918e0a31e6feaee19404, which implements the necessary null pointer validation. Additionally, monitoring systems should be configured to detect kernel panics or crashes related to graphics drivers, as these may indicate exploitation attempts. The fix also demonstrates adherence to ATT&CK technique T1499.004, which involves system disruption through kernel-level attacks, by providing proper error handling that prevents the escalation of memory access violations into complete system failures.