CVE-2026-53313 in Linux
Summary
by MITRE • 06/26/2026
In the Linux kernel, the following vulnerability has been resolved:
drm/amd/display: Avoid NULL dereference in dc_dmub_srv error paths
In dc_dmub_srv_log_diagnostic_data() and dc_dmub_srv_enable_dpia_trace().
Both functions check:
if (!dc_dmub_srv || !dc_dmub_srv->dmub)
and then call DC_LOG_ERROR() inside that block.
DC_LOG_ERROR() uses dc_dmub_srv->ctx internally. So if dc_dmub_srv is NULL, the logging itself can dereference a NULL pointer and cause a crash.
Fix this by splitting the checks.
First check if dc_dmub_srv is NULL and return immediately. Then check dc_dmub_srv->dmub and log the error only when dc_dmub_srv is valid.
Fixes the below: ../display/dc/dc_dmub_srv.c:962 dc_dmub_srv_log_diagnostic_data() error: we previously assumed 'dc_dmub_srv' could be null (see line 961) ../display/dc/dc_dmub_srv.c:1167 dc_dmub_srv_enable_dpia_trace() error: we previously assumed 'dc_dmub_srv' could be null (see line 1166)
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Analysis
by VulDB Data Team • 06/27/2026
This vulnerability resides in the AMD display driver component of the Linux kernel, specifically within the drm/amd/display subsystem where the dc_dmub_srv module handles display communication with the display microcontroller unit. The issue manifests as a NULL pointer dereference that occurs during error handling paths when diagnostic data logging and DPIA trace enabling functions attempt to process error conditions without proper validation of their input parameters. This represents a classic software reliability flaw where error handling code itself becomes a source of instability rather than a protective mechanism.
The technical flaw stems from improper conditional logic in two critical functions within the dc_dmub_srv module. Both dc_dmub_srv_log_diagnostic_data() and dc_dmub_srv_enable_dpia_trace() implement flawed validation sequences that check for NULL pointers but fail to properly separate the validation steps. The functions first verify that both dc_dmub_srv and dc_dmub_srv->dmub are non-NULL, yet they proceed to execute DC_LOG_ERROR() within this conditional block. However, DC_LOG_ERROR() internally references dc_dmub_srv->ctx which can cause a crash if dc_dmub_srv itself is NULL, effectively creating a scenario where error handling code becomes the source of system instability rather than preventing it.
This vulnerability directly corresponds to CWE-476_NULL_Pointer_Dereference, a well-documented weakness in software security where a program attempts to access memory through a null pointer reference. The operational impact of this flaw is significant as it can cause kernel crashes and system instability during normal operation or when diagnostic features are invoked. Attackers could potentially exploit this vulnerability by triggering error conditions in the display subsystem, leading to denial of service scenarios that might be particularly problematic in embedded systems or servers where continuous display functionality is critical.
The fix implemented addresses this issue by restructuring the validation logic to separate concerns properly. The corrected approach first validates whether dc_dmub_srv itself is NULL and returns immediately if so, preventing any further execution that could lead to pointer dereference. Only after establishing that the primary structure is valid does the code proceed to validate the dmub component and then execute logging operations. This approach follows fundamental software engineering principles of defensive programming and adheres to ATT&CK technique T1499.004 for avoiding system instability through proper error handling mechanisms.
The vulnerability affects systems running Linux kernels with AMD display drivers, particularly those implementing the dc_dmub_srv module for display communication with microcontroller units in modern graphics hardware. Systems that rely heavily on display diagnostics or DPIA tracing functionality would be most susceptible to exploitation of this flaw. The fix ensures that error paths remain stable regardless of input validation states and maintains system integrity even when unexpected NULL conditions occur during normal operation.
This type of vulnerability represents a common class of kernel-level flaws where developers assume certain safety conditions without proper validation, leading to scenarios where protective mechanisms become attack vectors themselves. The resolution demonstrates the importance of careful input validation in kernel code and highlights why error handling paths must be as robust as the main execution logic. Proper separation of validation steps prevents cascading failures and ensures that system stability is maintained even during exceptional conditions or malformed inputs.