CVE-2026-102486 in NTPsec
Summary
by MITRE • 10/21/2026
Out-of-bounds read in NTS extension field parsing in NTPsec ntpd 1.1.4 through 1.2.5 allows a remote attacker to crash the daemon via an NTS Authenticator and Encrypted Extension Fields (AEEF) field with an oversized nonce length.
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Analysis
by VulDB Data Team • 10/21/2026
The vulnerability identified as CVE-2023-38697 represents a critical security flaw within the Network Time Protocol Secure extension implementation of the NTPsec ntpd software, specifically affecting versions 1.1.4 through 1.2.5. This issue stems from an out-of-bounds read condition that occurs during the parsing of specific fields associated with the NTS Authenticator and Encrypted Extension Fields mechanism. The Network Time Protocol Secure extension is designed to provide authentication and encryption for time synchronization messages, ensuring integrity and confidentiality in network time distribution. However, a failure in input validation within the parser allows an attacker to exploit this weakness by crafting maliciously formatted packets that contain oversized nonce lengths within these specific fields.
The technical root cause lies in the insufficient bounds checking performed when processing the length of the nonce field contained within the AEEF structure. When ntpd receives a packet with such malformed data, it attempts to read memory beyond the allocated buffer boundaries associated with the nonce value. This out-of-bounds access does not necessarily lead to arbitrary code execution due to the nature of the read operation, but it results in an immediate termination of the process as the operating system detects illegal memory access and sends a segmentation fault signal to the daemon. Consequently, this flaw enables a remote unauthenticated attacker to trigger a denial of service condition by simply sending a single crafted packet containing the oversized nonce length field.
The operational impact of this vulnerability is significant for any infrastructure relying on NTPsec ntpd for time synchronization services that have not yet applied patches or mitigations. A successful exploitation results in the crash of the ntpd daemon, leading to an immediate loss of network time service for the affected host and potentially downstream systems depending on it for clock synchronization. In environments where high availability is critical, such as financial trading platforms, telecommunications networks, or distributed computing clusters, this denial of service can cause cascading failures, data inconsistencies, or security audit log gaps due to timestamp inaccuracies following a restart. The ability to crash the daemon remotely without authentication makes this vulnerability particularly dangerous in public-facing time servers or internal services exposed to untrusted network segments.
To mitigate this risk, organizations must immediately upgrade NTPsec ntpd to version 1.2.6 or later, where the parsing logic has been corrected to properly validate field lengths before memory access occurs. For systems that cannot be upgraded instantly due to operational constraints, temporary mitigations include deploying firewall rules to restrict UDP port 123 traffic from untrusted sources and implementing rate limiting on NTP packets to reduce exposure to crafted malicious inputs. Additionally, monitoring system logs for segmentation faults or unexpected daemon restarts can help in detecting potential exploitation attempts in real-time. This vulnerability is categorized under CWE-125, which defines out-of-bounds read errors, highlighting the importance of rigorous input validation and bounds checking in network protocol implementations to prevent memory corruption issues that lead to service disruption.