CVE-2023-53784 in Linux
Summary
by MITRE • 12/09/2025
In the Linux kernel, the following vulnerability has been resolved:
drm: bridge: dw_hdmi: fix connector access for scdc
Commit 5d844091f237 ("drm/scdc-helper: Pimp SCDC debugs") changed the scdc interface to pick up an i2c adapter from a connector instead. However, in the case of dw-hdmi, the wrong connector was being used to pass i2c adapter information, since dw-hdmi's embedded connector structure is only populated when the bridge attachment callback explicitly asks for it.
drm-meson is handling connector creation, so this won't happen, leading to a NULL pointer dereference.
Fix it by having scdc functions access dw-hdmi's current connector pointer instead, which is assigned during the bridge enablement stage.
[narmstrong: moved Fixes tag before first S-o-b and added Reported-by tag]
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Analysis
by VulDB Data Team • 03/29/2026
The vulnerability CVE-2023-53784 represents a critical null pointer dereference issue within the Linux kernel's display subsystem, specifically affecting the dw_hdmi bridge driver in the direct rendering manager framework. This flaw manifests in the scdc (Source Clock Domain) helper functionality where the system attempts to access an i2c adapter through an incorrect connector reference. The vulnerability stems from a code change in commit 5d844091f237 that modified how the scdc interface retrieves i2c adapter information by switching from a direct approach to one that depends on connector-based access. The fundamental issue occurs because the dw_hdmi driver maintains an embedded connector structure that remains unpopulated until the bridge attachment callback explicitly requests it, creating a timing dependency that can result in accessing uninitialized memory.
The technical implementation of this vulnerability involves a race condition between connector initialization and scdc helper execution. When drm-meson handles connector creation, it bypasses the normal bridge attachment callback sequence that would populate the embedded connector structure. This creates a scenario where scdc functions attempt to dereference a NULL pointer when trying to access the i2c adapter information through the improperly selected connector. The flaw specifically targets the drm/scdc-helper subsystem and demonstrates poor resource management practices where driver components depend on state that may not be initialized when required. The vulnerability is classified under CWE-476 as a NULL pointer dereference, representing a classic memory safety issue that can lead to system crashes and potential privilege escalation scenarios.
The operational impact of this vulnerability extends beyond simple system instability to potentially compromise the integrity of display subsystem operations in embedded and desktop environments. When triggered, the null pointer dereference causes kernel panics and system crashes, effectively rendering display functionality unavailable until system reboot. This affects devices using dw_hdmi bridges for HDMI output, including embedded systems, single-board computers, and desktop systems where the affected kernel versions are deployed. The vulnerability affects the broader drm subsystem and can be exploited by malicious actors to cause denial of service attacks against systems running affected kernel versions. The attack surface is particularly concerning in embedded environments where system availability is critical for proper device operation.
Mitigation strategies for CVE-2023-53784 focus on applying the kernel patch that corrects the connector access pattern by having scdc functions reference dw_hdmi's current connector pointer, which is properly assigned during the bridge enablement stage. System administrators should prioritize updating to kernel versions containing the fix, typically those incorporating the corrected commit 5d844091f237 and its associated changes. The fix addresses the underlying architectural issue by ensuring proper timing and state management between the bridge enablement process and scdc helper execution. Organizations should implement comprehensive testing procedures to validate that the patch does not introduce regressions in display functionality, particularly in systems using drm-meson drivers where connector creation is handled separately. Additionally, monitoring systems should be configured to detect potential exploitation attempts through kernel crash reports and system stability metrics, as this vulnerability can be leveraged for persistent denial of service attacks against critical infrastructure systems relying on HDMI display outputs.