CVE-2026-23076 in Linux
Summary
by MITRE • 02/04/2026
In the Linux kernel, the following vulnerability has been resolved:
ALSA: ctxfi: Fix potential OOB access in audio mixer handling
In the audio mixer handling code of ctxfi driver, the conf field is used as a kind of loop index, and it's referred in the index callbacks (amixer_index() and sum_index()).
As spotted recently by fuzzers, the current code causes OOB access at those functions. | UBSAN: array-index-out-of-bounds in /build/reproducible-path/linux-6.17.8/sound/pci/ctxfi/ctamixer.c:347:48 | index 8 is out of range for type 'unsigned char [8]'
After the analysis, the cause was found to be the lack of the proper (re-)initialization of conj field.
This patch addresses those OOB accesses by adding the proper initializations of the loop indices.
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Analysis
by VulDB Data Team • 05/03/2026
The vulnerability CVE-2026-23076 represents a critical out-of-bounds memory access flaw within the Linux kernel's ALSA subsystem, specifically affecting the ctxfi audio driver. This issue manifests in the context of audio mixer handling operations where the driver's implementation contains a fundamental initialization error that leads to memory corruption. The ctxfi driver, which is part of the Linux sound subsystem, manages audio mixer functionality for certain audio hardware configurations, making this vulnerability particularly concerning for systems utilizing affected audio hardware. The flaw exists in the ctamixer.c source file where the conf field is improperly used as a loop index without proper initialization, creating a scenario where memory accesses can extend beyond the allocated array boundaries.
The technical root cause of this vulnerability stems from inadequate initialization of the conj field within the audio mixer handling code, which serves as a loop counter in the context of index callbacks amixer_index() and sum_index(). When fuzzing tools analyzed the driver code, they identified that the conf field could reach a value of 8 while the target array is only 8 elements long, resulting in an out-of-bounds access at line 347 in the ctamixer.c file. This particular memory access pattern violates fundamental memory safety principles and creates opportunities for attackers to exploit the system through memory corruption. The vulnerability is classified as a CWE-129: Improper Validation of Array Index, which directly relates to the failure to validate that array indices are within acceptable bounds, and aligns with ATT&CK technique T1068: Exploitation for Privilege Escalation through kernel memory corruption.
The operational impact of this vulnerability extends beyond simple memory corruption, as it can potentially enable attackers to execute arbitrary code with kernel privileges or cause system instability through denial of service conditions. When the audio mixer handling code encounters an out-of-bounds access, the memory corruption can lead to unpredictable behavior including system crashes, data corruption, or more severe exploitation vectors. The vulnerability affects systems running Linux kernel versions that include the ctxfi driver, particularly those with audio hardware that utilizes this specific driver implementation. Attackers could potentially leverage this flaw by crafting malicious audio mixer operations or by triggering specific audio processing sequences that cause the driver to access memory beyond the intended array boundaries. The patch addressing this issue involves proper initialization of the loop indices to prevent the conf field from exceeding valid array boundaries, thereby eliminating the potential for out-of-bounds memory access and ensuring that the audio mixer handling operations remain within safe memory limits.