CVE-2015-1799 in ntpd
Summary
by MITRE
The symmetric-key feature in the receive function in ntp_proto.c in ntpd in NTP 3.x and 4.x before 4.2.8p2 performs state-variable updates upon receiving certain invalid packets, which makes it easier for man-in-the-middle attackers to cause a denial of service (synchronization loss) by spoofing the source IP address of a peer.
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Analysis
by VulDB Data Team • 05/02/2022
The vulnerability identified as CVE-2015-1799 resides within the Network Time Protocol daemon implementation, specifically in the ntpd software version 3.x and 4.x prior to 4.2.8p2. This flaw is categorized under the Common Weakness Enumeration as CWE-248, representing an unspecified flaw that can lead to unexpected behavior in protocol implementations. The issue manifests in the receive function of ntp_proto.c where the software processes incoming packets without proper validation of packet authenticity, creating a pathway for malicious actors to exploit the synchronization mechanisms that are fundamental to timekeeping in networked systems.
The technical execution of this vulnerability involves the manipulation of state variables within the NTP protocol implementation when processing invalid packets. During normal operation, ntpd maintains synchronization state information that tracks peer relationships and time synchronization metrics. When the receive function processes malformed or spoofed packets, it updates these internal state variables without adequate verification of packet legitimacy. This behavior creates a condition where an attacker can craft specific invalid packets that, when received by a vulnerable system, trigger inappropriate state transitions that ultimately result in synchronization loss.
The operational impact of this vulnerability extends beyond simple denial of service to represent a significant threat to network time synchronization integrity. Attackers exploiting this weakness can perform man-in-the-middle attacks by spoofing the source IP address of legitimate peers, effectively disrupting time synchronization across affected systems. The consequences include potential cascading failures in time-sensitive applications, compromised cryptographic operations that depend on accurate timekeeping, and broader network stability issues. This vulnerability particularly affects systems where precise time synchronization is critical, such as financial transaction systems, security infrastructure, and distributed computing environments.
Mitigation strategies for CVE-2015-1799 require immediate patching of affected NTP implementations to version 4.2.8p2 or later, which includes proper validation of packet state updates and enhanced protection against spoofed packet manipulation. Network administrators should implement additional security measures such as packet filtering to restrict NTP traffic to trusted sources, utilize authentication mechanisms like symmetric key cryptography with proper key management, and deploy intrusion detection systems to monitor for anomalous NTP packet patterns. The mitigation approach aligns with ATT&CK technique T1499.001 which addresses network denial of service attacks and emphasizes the importance of protocol-level defenses against manipulation of state variables in network services. Organizations should also consider implementing monitoring for unusual synchronization behavior and establish incident response procedures to address potential exploitation attempts.