CVE-2024-27436

What it actually does

Out-of-bounds write in ALSA USB audio channel map parsing when a device reports more channel bits than the actual channel count, allowing corruption of adjacent kernel memory.

Why it matters to the business

Local users on affected Linux systems can trigger kernel crashes or denial of service via specially crafted USB audio devices; widespread exposure in servers, desktops, and embedded devices using the ALSA USB driver increases operational risk until patched.

How an attack unfolds

An attacker with local access connects a malicious or malformed USB audio device that advertises more channel bits than its actual channel count; the kernel continues parsing beyond the map array bounds, corrupting memory and causing a crash or potential escalation.

How to fix it

Update the Linux kernel to a version containing commit 7e2c1b0f6dd9abde9e60f0f9730026714468770f or later; rebuild and reboot with the patched kernel. For distributions, apply the corresponding security update that backports the fix.

How to confirm the fix worked

Verify the running kernel contains the fix commit or is newer than the vulnerable versions; test with a USB audio device that previously triggered excess channel bits and confirm no out-of-bounds write occurs.

Typical attack path

1. Obtain local user access on a Linux system
2. Attach a USB audio device that sets excess channel bits in its descriptor
3. Trigger ALSA USB audio initialization and channel map parsing
4. Observe kernel memory corruption leading to denial of service

How to detect it

Review kernel logs for ALSA USB audio oops or panic messages referencing channel map parsing; inspect dmesg and syslog for USB descriptor parsing failures around device connect events.

What your security team should do

• Prioritize kernel updates on all Linux systems exposing USB audio functionality
• Restrict untrusted USB device attachment via policy or hardware controls until patched
• Monitor for kernel oops or panics involving ALSA USB audio after device insertion