CVE-2025-38729

What it actually does

The vulnerability allows out-of-bounds memory accesses in the ALSA usb-audio driver when processing UAC3 power domain descriptors whose bLength field is not validated against the actual descriptor size.

Why it matters to the business

Linux systems handling USB audio devices can be compromised by malicious firmware, leading to kernel-level memory corruption that may enable local privilege escalation or denial of service on affected endpoints.

How an attack unfolds

An attacker supplies a malicious USB audio device containing a crafted UAC3 power domain descriptor with an invalid bLength value. When the kernel parses the descriptor without length validation, it performs out-of-bounds reads or writes, potentially allowing code execution or further privilege escalation within the kernel context.

How to fix it

Update the Linux kernel to a version containing commit 1666207ba0a5973735ef010812536adde6174e81 or later stable releases that include the UAC3 power domain descriptor validation fix.

How to confirm the fix worked

Verify the running kernel contains commit 1666207ba0a5973735ef010812536adde6174e81 by checking git log or kernel version strings after applying updates; test with known-good UAC3 devices to confirm descriptor parsing succeeds without crashes.

Typical attack path

1. Attacker crafts a USB device with a malformed UAC3 power domain descriptor
2. Device is connected to a vulnerable Linux system
3. Kernel usb-audio driver parses the descriptor without validating bLength
4. Out-of-bounds memory access occurs leading to corruption
5. Attacker leverages corruption for privilege escalation or system instability

How to detect it

Review kernel logs for usb-audio or ALSA errors during USB device enumeration; look for unexpected crashes or OOB-related warnings when connecting USB audio hardware; correlate with physical device insertion timestamps.

What your security team should do

• Prioritize kernel updates to the fixed commit across all Linux distributions and embedded devices using ALSA usb-audio
• Restrict physical USB device access on high-risk systems until patched
• Monitor for USB audio device connection events in system logs as part of broader endpoint hardening