NTP BUG 3377: Buffer Overflow in ntpq when fetching reslist from a malicious ntpd
Last update: April 22, 2024 18:49 UTC (7e7bd5857)
Summary
Description
A stack buffer overflow in ntpq can be triggered by a malicious ntpd server when ntpq requests the restriction list from the server. This is due to a missing length check in the reslist() function. It occurs whenever the function parses the server’s response and encounters a flagstr variable of an excessive length. The string will be copied into a fixed-size buffer, leading to an overflow on the function’s stack-frame.
Note well that this problem requires a malicious server, and affects ntpq, not ntpd.
Mitigation
- Upgrade to 4.2.8p10 or later.
- If you can’t upgrade your version of
ntpq then if you want to know the reslist of an instance of ntpd that you do not control, know that if the target ntpd is malicious that it can send back a response that intends to crash your ntpq process.
Credit
This weakness was discovered by Cure53.
Timeline