CVE-2024-57893

What it actually does

Race condition in ALSA sequencer OSS layer when reassembling SysEx messages from 6-byte packets allows concurrent access to an internal buffer, resulting in out-of-bounds memory access.

Why it matters to the business

Linux systems handling MIDI SysEx traffic via OSS sequencer may experience kernel instability or crashes; low EPSS and no KEV listing indicate limited active exploitation risk despite mentions in broad 2024 espionage and financial campaigns, with impact primarily on audio/MIDI workloads in affected Ubuntu LTS releases and upstream kernels.

How an attack unfolds

An attacker with local access triggers rapid SysEx packet delivery to the OSS sequencer while another thread accesses the shared buffer, winning the race to cause out-of-bounds read/write; listed threat actors in Linux kernel campaigns could leverage similar timing windows for escalation though this specific CVE shows no confirmed actor usage.

How to fix it

Upgrade to fixed versions: apr 1.5.0-1ubuntu0.1~esm1 on Ubuntu Pro 14.04 LTS, 1.5.2-3ubuntu0.1~esm1 on 16.04 LTS, 1.6.3-2 on 18.04 LTS; apply Linux kernel commit cff1de87ed14fc0f2332213d2367100e7ad0753a or later stable releases containing the mutex serialization for SysEx processing.

How to confirm the fix worked

Confirm package versions match the listed fixed releases, verify presence of mutex around SysEx buffer handling in ALSA OSS code, and test SysEx message streams under concurrent load for absence of OOB faults.

Typical attack path

1. Obtain local user access on affected Linux system
2. Open OSS sequencer device and begin sending fragmented SysEx messages
3. Concurrently trigger buffer access from another process or thread
4. Win race condition to trigger out-of-bounds access and potential kernel compromise

How to detect it

Review kernel logs for ALSA sequencer OOB warnings or crashes during SysEx processing; inspect process activity involving /dev/sequencer or OSS MIDI devices around the time of anomalies; correlate with listed Linux kernel privilege escalation campaigns for similar timing-based artifacts.

What your security team should do

• Prioritize patching Ubuntu LTS systems running ALSA/OSS sequencer workloads within CISA-style timelines even without KEV listing
• Audit systems for MIDI/SysEx usage and restrict untrusted local access to sequencer devices
• Monitor EPSS trend (stable at 0.0018) and update threat intel feeds for any new actor exploitation of similar kernel races