CVE-2026-98744 Overview
CVE-2026-98744 is a Linux kernel vulnerability in the ASoC (ALSA System on Chip) max98363 codec driver. The driver passes an uninitialized stream_config structure to sdw_stream_add_slave(). The type field may contain stack garbage, which sdw_config_stream() subsequently copies into stream->type. Zero-initializing stream_config so type defaults to SDW_STREAM_PCM resolves the defect. The fix has been merged into stable kernel branches.
Critical Impact
Uninitialized memory use in a SoundWire codec path can produce inconsistent stream behavior and may be leveraged for information exposure or audio subsystem instability on affected Linux systems.
Affected Products
- Linux kernel – ASoC max98363 codec driver
- Stable kernel branches patched via commits 1c251426bb67, 7df8c39a50f3, a756c93fae31, bcd61aa247c2, and f44ba04c7a32
- Linux distributions shipping vulnerable stable kernel versions prior to the referenced fixes
Discovery Timeline
- 2026-10-18 - CVE-2026-98744 published to NVD
- 2026-10-21 - Last updated in NVD database
Technical Details for CVE-2026-98744
Vulnerability Analysis
The defect lives in the max98363 SoundWire codec driver under sound/soc/codecs/. The driver declares a stream_config structure on the stack and passes it to sdw_stream_add_slave() without initialization. The SoundWire core function sdw_config_stream() reads the type member and copies it into stream->type. Because stream_config was never zeroed, type contains whatever residual data occupied that stack region.
This is a classic uninitialized memory use pattern. Downstream SoundWire logic branches on stream->type to choose between PCM and PDM handling. A garbage value can produce incorrect routing, audio glitches, or an inconsistent stream state. In some execution paths, uninitialized values can also expose kernel stack contents to user-visible structures.
The upstream fix zero-initializes stream_config so type defaults to SDW_STREAM_PCM, which matches the driver's intended behavior.
Root Cause
The root cause is missing initialization of an on-stack structure before it is consumed by a kernel API that trusts the structure's fields. The max98363 driver did not apply the common pattern of designated or zero initialization for struct sdw_stream_config. This falls under uninitialized memory use, closely related to [CWE-457].
Attack Vector
The affected code path is reached during SoundWire slave stream configuration on hardware using the max98363 amplifier. Reaching the vulnerable function requires the driver to be loaded and a SoundWire stream to be configured. In practice, exploitation requires local access on systems with the affected codec present. No evidence of remote exploitation exists, and no public exploit code is available.
See the upstream patches for the exact source change: Kernel Patch 1c251426bb67 and Kernel Patch f44ba04c7a32.
Detection Methods for CVE-2026-98744
Indicators of Compromise
- No specific runtime indicators of compromise are published for this defect.
- Unexpected audio stream type mismatches or SoundWire configuration errors in dmesg on systems using the max98363 codec may indicate the uninitialized value is being consumed.
Detection Strategies
- Inventory running kernel versions and compare against the patched stable commits referenced in the NVD entry.
- Scan build configurations for CONFIG_SND_SOC_MAX98363=y or =m on hosts where the driver is actually loaded.
- Use static analyzers such as Smatch or Coccinelle to flag struct sdw_stream_config declarations without zero initialization in downstream forks.
Monitoring Recommendations
- Monitor kernel logs for ASoC and SoundWire warnings referencing sdw_stream_add_slave or sdw_config_stream.
- Track distribution security advisories for backported fixes to long-term support kernels.
- Record kernel version changes through configuration management to confirm patch rollout.
How to Mitigate CVE-2026-98744
Immediate Actions Required
- Update to a Linux stable kernel that includes one of the referenced fix commits.
- Rebuild and reboot systems where the max98363 codec driver is loaded.
- For custom kernels, cherry-pick the upstream patch into local trees before shipping new builds.
Patch Information
The fix zero-initializes stream_config in the max98363 codec driver so type defaults to SDW_STREAM_PCM. The change is distributed across these stable branch commits: Kernel Patch 1c251426bb67, Kernel Patch 7df8c39a50f3, Kernel Patch a756c93fae31, Kernel Patch bcd61aa247c2, and Kernel Patch f44ba04c7a32.
Workarounds
- Unload or blacklist the snd_soc_max98363 module on systems that do not require the codec.
- Disable CONFIG_SND_SOC_MAX98363 in custom kernel builds where the hardware is not present.
- Restrict local access to systems that cannot be patched immediately to reduce exposure to local triggers.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
