CVE-2024-39491

What it actually does

Use-after-free in ALSA HDA cs35l56 driver caused by cs_dsp instance initialized in probe() but lifetime managed incorrectly via component unbind callback, allowing use of freed or uninitialized instance on rebind or error paths.

Why it matters to the business

Kernel instability or potential privilege escalation on Linux systems using affected Cirrus Logic HDA codecs; low exploitability reduces urgency but still requires kernel updates to avoid crashes during audio device hotplug or driver reload.

How an attack unfolds

An attacker with local access triggers repeated driver probe/remove or component bind/unbind sequences to force use of a freed cs_dsp instance, leading to memory corruption that may be leveraged for code execution.

How to fix it

Update Linux kernel to commit 9054c474f9c219e58a441e401c0e6e38fe713ff1 or later stable release containing the cs_dsp lifetime fix; ensure cs_dsp_remove() is called in remove() and error paths of cs35l56_hda_common_probe().

How to confirm the fix worked

Verify presence of the fix commit in kernel source; test probe/remove and bind/unbind cycles on affected hardware to confirm no use of uninitialized cs_dsp; monitor for related kernel warnings during driver load.

Typical attack path

1. Gain local access to system with vulnerable cs35l56 HDA codec
2. Trigger driver unload or component unbind
3. Re-bind or reload driver to access uninitialized cs_dsp
4. Perform operations that dereference freed memory
5. Escalate via resulting kernel memory corruption

How to detect it

Search kernel logs for cs35l56, cs_dsp, and use-after-free or uninitialized memory warnings during module load/unload; inspect dmesg for component bind failures on systems with Cirrus Logic HDA codecs.

• cs35l56_hda_common_probe
• cs35l56_hda_unbind
• cs_dsp instance uninitialized

What your security team should do

• Apply the referenced kernel commit immediately on systems with cs35l56 hardware
• Audit audio driver reload and hotplug handling in production kernels
• Monitor EPSS and threat actor activity for any rise in exploit maturity
• Prioritize kernel updates in environments with frequent device attach/detach