CVE-2026-102484 in NTPsec
Summary
by MITRE • 10/21/2026
Heap-based buffer overflow in the JJY refclock driver in NTPsec ntpd before 1.2.6 allows an attacker who controls the Telephone JJY time source to corrupt memory or crash ntpd via more than six time replies.
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Analysis
by VulDB Data Team • 10/21/2026
The vulnerability identified as a heap-based buffer overflow within the JJY refclock driver of NTPsec's ntpd daemon prior to version 1.2.6 represents a critical security flaw that compromises the integrity and availability of network time synchronization services. The Network Time Protocol is fundamental for maintaining accurate system clocks across distributed computing environments, ensuring consistency in logging, authentication, and transaction processing. When an instance of ntpd operates with support for the JJY radio clock driver, it attempts to synchronize its internal clock by interpreting signals from Japanese low-frequency radio stations that broadcast time information via pulse position modulation. The specific defect resides in how the software processes incoming data packets from this specialized hardware interface or simulated source, particularly when handling multiple consecutive time replies exceeding a threshold of six messages.
From a technical perspective, the root cause is classified under CWE-122, which denotes a heap-based buffer overflow. This type of vulnerability occurs when a program writes more data to a block of memory allocated on the heap than it can hold. In this specific context, the JJY refclock driver fails to adequately validate or bound-check the length of incoming time reply structures before copying them into fixed-size buffers. An attacker who controls the Telephone JJY time source, effectively acting as a man-in-the-middle or controlling the radio signal reception environment, can craft maliciously formatted packets containing excessive data payloads. Upon receiving more than six such replies in quick succession, the driver attempts to write this oversized input into a pre-allocated heap buffer without verifying that the destination memory region is sufficiently large to accommodate the excess bytes.
The operational impact of exploiting this flaw is severe and multifaceted. The immediate consequence is the corruption of adjacent memory structures on the heap, which can lead to unpredictable application behavior or a complete crash of the ntpd process. A denial-of-service condition arises as the daemon terminates unexpectedly, disrupting time synchronization for all systems relying on that server. More critically, because modern operating systems employ various mitigations such as Address Space Layout Randomization and non-executable stacks, attackers often leverage heap overflows to achieve arbitrary code execution rather than simple crashes. By carefully crafting the overflow payload, an attacker can overwrite function pointers or object metadata within the heap structure. This manipulation allows for the redirection of program control flow, potentially leading to remote code execution with the privileges of the ntpd process. Given that ntpd often runs with elevated permissions to adjust system time and may bind to network interfaces, successful exploitation could grant an attacker significant access to the underlying operating system.
This vulnerability aligns with MITRE ATT&CK technique T1059, specifically Command and Scripting Interpreter sub-techniques if code execution is achieved through script injection via memory corruption, or more broadly under privilege escalation vectors where the compromised service account provides a foothold for further lateral movement. The attack vector involves network interaction but requires specific control over the time source signal path, which might be feasible in scenarios involving spoofed radio signals or compromised local hardware interfaces used by the NTP client software.
Mitigation strategies must prioritize immediate patching to version 1.2.6 or later of NTPsec ntpd, where developers have implemented proper bounds checking and input validation within the JJY refclock driver logic. Administrators should verify that their systems are updated through official package managers or source compilation processes provided by the upstream maintainers. In environments where immediate patching is not feasible due to operational constraints, temporary mitigations include disabling the JJY refclock module if it is not actively required for time synchronization purposes. This can be achieved by removing the driver from the configuration file or compiling ntpd without support for this specific hardware interface. Additionally, deploying network intrusion detection systems that monitor for anomalous patterns in NTP traffic may help identify attempted exploitation activities, although such measures are secondary to addressing the underlying code defect through software updates. Regular security audits and static analysis of custom drivers used by critical infrastructure services like time synchronization daemons are recommended to prevent similar memory safety issues from persisting in production environments.