CVE-2020-16123

What it actually does

Race condition in Ubuntu PulseAudio snap policy module allows client connections from snaps to bypass identification when SCM_CREDENTIALS are absent, breaking confinement and enabling exposure of sensitive audio information.

Why it matters to the business

On Ubuntu systems using snaps for audio applications, attackers with local access can leak sensitive information, raising data exposure risk in desktop and server environments where snap isolation is relied upon for security boundaries.

How an attack unfolds

An attacker installs or runs a malicious snap on an affected Ubuntu system and triggers the race condition by omitting SCM_CREDENTIALS during PulseAudio connection setup, causing the policy module to fail to recognize the snap origin and grant unconfined access to audio streams and related data.

How to fix it

Upgrade PulseAudio to a fixed version such as 1:13.99.3-1ubuntu2, 1:13.99.2-1ubuntu2.1, 1:13.99.1-1ubuntu3.8, 1:11.1-1ubuntu7.11, or 1:8.0-0ubuntu3.15 depending on the Ubuntu release in use.

How to confirm the fix worked

Verify installed PulseAudio package version matches a fixed release, then test snap client connections under simulated missing-credential conditions to confirm policy enforcement.

Typical attack path

1. Obtain local access or deploy a malicious snap package
2. Initiate PulseAudio client connection while omitting SCM_CREDENTIALS
3. Exploit timing window in snap policy module to bypass confinement check
4. Connect without proper isolation and access sensitive audio information

How to detect it

Review system and PulseAudio logs for anomalous client connection attempts lacking credential data or policy bypass indicators; correlate with snap execution events on affected hosts.

What your security team should do

• Apply the listed PulseAudio package updates across all Ubuntu systems
• Audit snap usage and restrict untrusted snaps pending updates
• Enable additional logging for PulseAudio client connections to support monitoring