CVE-2021-3899

What it actually does

Race condition in replaced executable detection logic allows a local attacker with appropriate configuration to inject and execute arbitrary code with root privileges.

Why it matters to the business

Local attackers can gain full administrative control over affected systems, enabling data theft, persistence, or disruption of critical services.

How an attack unfolds

An attacker with local access configures the environment to trigger executable replacement detection, then wins the race window to substitute malicious code that executes as root.

How to fix it

Apply vendor patches that eliminate the race condition in replaced executable detection; review and harden local configuration settings that enable the feature.

How to confirm the fix worked

Confirm systems are running patched versions; audit configurations for the replaced executable detection feature and test for race condition exposure in controlled environments.

Typical attack path

1. Obtain local access to a system with the vulnerable configuration enabled
2. Prepare a malicious executable and trigger the replacement detection path
3. Exploit the timing window to replace the detected executable
4. Execute the injected code with elevated root privileges

How to detect it

Review system logs for anomalous executable replacement events, unexpected root-owned processes, and timing anomalies around file modification operations.

What your security team should do

• Apply available patches immediately on all affected systems
• Disable or restrict the replaced executable detection feature where possible
• Enforce least-privilege execution and monitor for unexpected root process spawns