CVE-2015-5146

What it actually does

Improper input validation in ntpd allows a remote authenticated user with the configuration password to supply a crafted configuration directive containing a NULL byte, resulting in a service crash when remote configuration is enabled.

Why it matters to the business

Disruption of time synchronization services can cause operational outages, affect logging accuracy, certificate validation, and scheduled tasks across dependent systems; the vulnerability is old with modest exploitation probability and no known ransomware usage.

How an attack unfolds

An attacker who knows the remote configuration password and can reach a host permitted to perform remote configuration sends a specially crafted directive packet containing a NULL byte; the server fails to handle the malformed input and crashes.

How to fix it

Upgrade ntpd to version 4.2.8p3 or later; if remote configuration is not required, disable it via the configuration file and restart the service.

How to confirm the fix worked

Verify ntpd version is 4.2.8p3 or newer; confirm remote configuration is disabled or test that malformed directive packets no longer cause crashes in a lab environment.

Typical attack path

1. Obtain the ntpd remote configuration password
2. Gain network access from a host trusted for remote configuration
3. Craft and transmit a configuration directive packet containing an embedded NULL byte
4. Trigger service crash and denial of service

How to detect it

Review ntpd logs for unexpected restarts or crashes around the time of configuration directive processing; examine network traffic or configuration logs for unusual directive packets from authorized hosts.

What your security team should do

• Prioritize upgrade of all ntpd instances to 4.2.8p3 or later
• Audit configurations and disable remote configuration where feasible
• Monitor EPSS trend and reassess if exploitation activity increases