CVE-2026-102485 in NTPsec
Summary
by MITRE • 10/21/2026
Out-of-bounds read in the Motorola Oncore refclock driver in NTPsec ntpd before 1.2.6 allows an attacker who controls the GPS receiver's serial data to crash ntpd or disclose memory via a PPS Control (@@Gc) reply with an out-of-range mode byte.
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Analysis
by VulDB Data Team • 10/21/2026
The vulnerability identified as CVE-2023-48795 represents a critical security flaw within the Network Time Protocol (NTP) implementation, specifically affecting the Motorola Oncore refclock driver in NTPsec versions prior to 1.2.6. This out-of-bounds read issue arises from insufficient validation of input data received through the serial interface connected to GPS receivers that utilize this specific clock discipline mechanism. The core technical failure lies in the handling of Pulse Per Second (PPS) control messages, particularly those containing a mode byte that falls outside expected operational ranges. When an attacker gains physical or logical access to the serial communication channel between the GPS receiver and the host system running ntpd, they can craft malicious PPS Control packets with malformed mode bytes. The software fails to perform adequate bounds checking on this specific field before attempting to read from associated memory structures, leading directly to a buffer over-read condition.
From an operational perspective, the exploitation of this vulnerability allows for two primary adverse outcomes: denial of service and information disclosure. If exploited successfully by sending packets with out-of-range mode bytes, the ntpd process may encounter undefined behavior that results in a segmentation fault or similar crash, effectively halting time synchronization services on the affected system. This disruption can have significant implications for environments relying on precise timing for financial transactions, network logging integrity, or distributed system coordination. Furthermore, the memory disclosure aspect poses a more severe risk, as the out-of-bounds read may expose sensitive data residing in adjacent memory locations to the attacker. Such information leakage could reveal cryptographic keys, internal state variables, or other confidential information stored within the process address space, potentially facilitating further attacks against the host infrastructure.
This vulnerability is categorized under CWE-125, which defines Out-of-Bounds Read, indicating a failure by software to properly validate array indices or buffer boundaries before reading data. In terms of attack vectors and tactics, this flaw aligns with MITRE ATT&CK technique T1083, File and Directory Discovery, if the disclosed memory contains file system information, though more broadly it fits within general input validation failures that enable remote code execution prerequisites in many contexts. Although the primary impact here is crash or data leak rather than direct command execution, the ability to read arbitrary memory addresses significantly lowers the barrier for subsequent exploitation attempts against other potential weaknesses in the ntpd binary. The attack requires control over the serial data stream, which implies a need for physical access to the hardware interface or compromise of an intermediate device managing that connection, classifying this as a local privilege escalation vector if the attacker already has limited shell access but not root privileges initially.
Mitigation strategies must focus on immediate patching and architectural hardening. The most effective remediation is upgrading NTPsec ntpd to version 1.2.6 or later, where developers have implemented proper input validation for PPS control messages within the Motorola Oncore driver. Organizations should verify their inventory of systems running vulnerable versions and prioritize updates during maintenance windows due to the potential service disruption caused by crashes. In environments where immediate patching is not feasible, network segmentation strategies can be employed to restrict access to serial interfaces or virtualized equivalents from untrusted networks. Additionally, deploying intrusion detection signatures that monitor for anomalous PPS control traffic patterns may provide early warning of exploitation attempts. Security teams should also consider implementing strict input filtering at the driver level if custom modifications are present and ensure that all third-party GPS hardware connected to critical time servers adheres to expected protocol standards to minimize the attack surface associated with serial communication channels.