CVE-2020-11868 is a medium-severity vulnerability affecting the Network Time Protocol daemon (ntpd) versions prior to 4.2.8p14 and 4.3.x versions before 4.3.100. The vulnerability arises because ntpd improperly handles server mode packets that lack a valid origin timestamp. Specifically, an off-path attacker—meaning an attacker who does not have direct access to the communication channel—can send spoofed server mode packets with a forged source IP address to the ntpd service. These packets cause ntpd to reschedule transmissions unnecessarily, effectively blocking unauthenticated synchronization attempts. This behavior can be exploited to disrupt time synchronization services by preventing clients from successfully synchronizing their clocks with legitimate NTP servers. The vulnerability does not allow for compromise of confidentiality or integrity of the time data, nor does it require authentication or user interaction. However, it impacts availability by enabling denial-of-service (DoS) conditions on time synchronization. The CVSS 3.0 score of 5.9 reflects a medium severity, with a high attack complexity (AC:H), no privileges required (PR:N), no user interaction (UI:N), and no impact on confidentiality or integrity, but high impact on availability (A:H). The underlying weakness corresponds to CWE-346 (Origin Validation Error), indicating insufficient validation of the origin timestamp in NTP packets. No known exploits are currently reported in the wild, and no official patches are linked in the provided data, though it is expected that updated ntpd versions address this issue.

For European organizations, the impact of CVE-2020-11868 primarily concerns the availability and reliability of time synchronization services. Accurate timekeeping is critical for many security mechanisms, including logging, authentication protocols (e.g., Kerberos), certificate validation, and event correlation. Disruption of NTP synchronization can lead to time drift, causing failures in these systems and potentially complicating incident response and forensic investigations. Industrial control systems, financial institutions, telecommunications, and critical infrastructure sectors in Europe rely heavily on precise time synchronization. An attacker exploiting this vulnerability could cause intermittent or sustained denial-of-service conditions on NTP services, leading to operational disruptions. Although the attack does not compromise data confidentiality or integrity, the availability impact can degrade trust in system logs and security controls. Given the medium severity and the requirement for off-path spoofing capabilities, the threat is moderate but should not be underestimated, especially in environments where NTP is unauthenticated and exposed to untrusted networks.

To mitigate CVE-2020-11868, European organizations should implement the following specific measures: 1) Upgrade ntpd to versions 4.2.8p14 or later, or 4.3.100 or later, where this vulnerability is addressed. 2) Configure NTP to use authentication mechanisms such as symmetric key or Autokey to prevent unauthenticated synchronization attempts. 3) Restrict NTP traffic to trusted networks and servers by implementing firewall rules that block NTP packets from untrusted or external IP addresses, thereby reducing the risk of spoofed packets reaching ntpd. 4) Employ network ingress filtering (e.g., BCP38) to prevent IP spoofing within the organization's network perimeter. 5) Monitor NTP service logs and network traffic for unusual patterns indicative of spoofed or malformed packets causing rescheduling behavior. 6) Consider deploying alternative time synchronization protocols or services with stronger security features, such as NTS (Network Time Security), where feasible. These targeted mitigations go beyond generic advice by focusing on authentication, network filtering, and monitoring tailored to the nature of this vulnerability.