CVE-2023-26555

What it actually does

Out-of-bounds write in praecis_parse within ntpd/refclock_palisade.c allowing memory corruption when processing specially crafted input from a GPS receiver.

Why it matters to the business

Compromise of time synchronization services could disrupt operations in environments relying on accurate time, though the attack requires physical access or a manipulated GPS device and is complex to execute.

How an attack unfolds

An attacker with access to a compatible GPS receiver manipulates the device to send malformed data that triggers the out-of-bounds write during parsing in the NTP daemon, leading to memory corruption that may be leveraged for code execution or denial of service.

How to fix it

Upgrade NTP to a version containing a corrected praecis_parse implementation or apply distribution-specific patches; disable the Palisade refclock driver if the hardware is not required.

How to confirm the fix worked

Confirm the installed NTP version and inspect refclock_palisade.c to verify the presence of bounds checks in praecis_parse; test with known-good and malformed GPS input streams in a lab environment.

Typical attack path

1. Obtain physical or adjacent access to a Palisade-compatible GPS receiver connected to the target NTP server
2. Craft and inject malformed binary or NMEA data from the receiver
3. Trigger praecis_parse in ntpd to perform the out-of-bounds write
4. Exploit resulting memory corruption to execute arbitrary code or crash the daemon

How to detect it

Review ntpd logs and system crash reports for anomalies originating from refclock_palisade parsing; correlate with GPS receiver hardware events or unexpected time jumps.

What your security team should do

• Inventory systems using the Palisade refclock and assess exposure
• Apply available NTP updates or vendor patches immediately
• Disable unused GPS refclocks and prefer authenticated time sources
• Monitor upstream NTP releases for future fixes given the absence of listed fixed versions