CVE-2026-98744 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
ASoC: codecs: max98363: fix uninitialized stream_config->type
stream_config is not initialized before being passed to sdw_stream_add_slave(). The type field may contain garbage and is later copied to stream->type by sdw_config_stream().
Zero-initialize stream_config so type defaults to SDW_STREAM_PCM.
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Analysis
by VulDB Data Team • 10/18/2026
The Linux kernel audio subsystem, specifically the Advanced SoC Codec driver for Maxim Integrated MAX98363 devices, contained a critical initialization flaw within its SoundWire interface implementation. The vulnerability stems from an uninitialized local variable named stream_config prior to its usage in the sdw_stream_add_slave function call. In C programming, local variables that are not explicitly initialized contain indeterminate values, often referred to as garbage data, which reside on the stack at the time of allocation. This oversight creates a scenario where subsequent operations rely on unpredictable state rather than defined defaults, leading to potential instability or incorrect behavior in audio stream configuration processes.
The technical mechanism of this flaw involves the sdw_stream_add_slave function accepting an uninitialized structure pointer. Within this context, the type field of the stream_config structure is accessed and subsequently passed down the call chain. The downstream function sdw_config_stream then copies this potentially corrupted value into the persistent stream->type member. Because the initial value was not set to a known good state, the resulting stream configuration may reflect arbitrary memory contents rather than the intended protocol type. This lack of explicit initialization violates fundamental principles of safe software development and introduces non-deterministic behavior into the kernel's audio pipeline management logic.
From an operational perspective, this vulnerability can manifest as audio playback or recording failures on systems utilizing MAX98363 codecs over SoundWire interfaces. The undefined stream type may cause the driver to misinterpret how data should be formatted or transmitted, leading to corrupted audio output, silence, or system crashes if the garbage value triggers invalid memory access patterns in downstream processing routines. While immediate exploitation for arbitrary code execution is unlikely given that this primarily affects internal state configuration rather than direct user input handling, it represents a significant reliability issue and potential denial of service vector through kernel instability during device initialization or stream setup phases.
This flaw aligns with CWE-457, which describes the use of an uninitialized variable as a weakness category. The failure to properly initialize data structures before their first use is a common source of bugs in systems programming languages like C and often serves as a precursor to more severe vulnerabilities if the garbage value influences control flow or memory safety checks. Addressing this issue requires ensuring that all local variables are explicitly initialized at declaration or immediately prior to usage, thereby eliminating reliance on stack remnants from previous function calls.
The remediation for this vulnerability involves zero-initializing the stream_config structure before it is passed to sdw_stream_add_slave. By setting the memory contents to zero, the type field defaults to SDW_STREAM_PCM, which is a valid and expected state for standard audio streams in this context. This fix ensures deterministic behavior regardless of prior stack conditions. Security best practices dictate that developers should always initialize variables explicitly rather than relying on implicit behaviors or assumptions about compiler optimizations. Implementing static analysis tools configured to detect uninitialized variable usage can help prevent similar issues in future code changes, reinforcing the integrity of kernel subsystems against such elementary but impactful errors.