CVE-2023-52806 in Linux
Summary
by MITRE • 05/21/2024
In the Linux kernel, the following vulnerability has been resolved:
ALSA: hda: Fix possible null-ptr-deref when assigning a stream
While AudioDSP drivers assign streams exclusively of HOST or LINK type, nothing blocks a user to attempt to assign a COUPLED stream. As supplied substream instance may be a stub, what is the case when code-loading, such scenario ends with null-ptr-deref.
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Analysis
by VulDB Data Team • 05/21/2024
The vulnerability CVE-2023-52806 represents a critical null pointer dereference issue within the Linux kernel's Advanced Linux Sound Architecture subsystem, specifically affecting the HD-audio driver component. This flaw exists in the stream assignment mechanism where the system fails to properly validate stream types during the assignment process. The vulnerability manifests when AudioDSP drivers attempt to assign streams, particularly when dealing with COUPLED stream types that are not properly handled by the existing validation logic.
The technical root cause stems from insufficient input validation within the HD-audio driver's stream assignment code. When a user attempts to assign a COUPLED stream type, the system does not adequately verify whether the substream instance is valid or complete. During code-loading scenarios, substream instances may be in a stub state, meaning they lack proper initialization or memory allocation. This incomplete state creates a situation where a null pointer reference occurs when the system attempts to dereference a pointer that points to no valid memory location, resulting in a kernel panic or system crash.
This vulnerability directly relates to CWE-476, which describes null pointer dereference conditions that can lead to system instability and potential privilege escalation. The flaw operates at the kernel level within the ALSA subsystem, making it particularly dangerous as it can affect system stability and potentially provide attack vectors for malicious actors. The issue specifically impacts the HD-audio driver's handling of stream assignments, where the code path does not properly account for stub substream instances that may occur during system initialization or code loading phases.
The operational impact of this vulnerability extends beyond simple system crashes, as it can lead to complete system instability and denial of service conditions. When the null pointer dereference occurs during audio stream assignment, it can cause the entire audio subsystem to become unavailable, potentially affecting critical system functions that depend on proper audio handling. Attackers could exploit this vulnerability by crafting malicious audio stream assignments that force the system into a null pointer dereference state, leading to system crashes or potentially allowing for privilege escalation depending on the system configuration.
Mitigation strategies for CVE-2023-52806 should focus on implementing proper input validation and null pointer checks within the HD-audio driver's stream assignment code. The fix involves adding comprehensive validation to ensure that substream instances are properly initialized before attempting any stream assignment operations. Security teams should prioritize applying the kernel patches released by the Linux kernel security team, which address the specific null pointer dereference issue by validating stream types and ensuring that stub substream instances are properly handled. Additionally, system administrators should monitor for any unusual audio stream assignment patterns that might indicate exploitation attempts, as this vulnerability can be leveraged to disrupt audio functionality and potentially gain unauthorized system access through carefully crafted audio stream assignments that trigger the null pointer dereference condition.