CVE-2023-26554 in NTP
Summary
by MITRE • 04/12/2023
mstolfp in libntp/mstolfp.c in NTP 4.2.8p15 has an out-of-bounds write when adding a '\0' character.
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Analysis
by VulDB Data Team • 04/29/2026
The vulnerability identified as CVE-2023-26554 resides within the Network Time Protocol implementation in NTP 4.2.8p15, specifically within the mstolfp function located in libntp/mstolfp.c. This flaw represents a critical out-of-bounds write condition that can be triggered during the processing of string inputs containing null characters. The vulnerability manifests when the system attempts to add a null character to a buffer without proper bounds checking, creating an opportunity for memory corruption that could potentially be exploited by malicious actors.
The technical implementation of this vulnerability stems from insufficient input validation and buffer management within the mstolfp function. When processing time synchronization data, the function fails to properly validate the length of input strings before attempting to write data containing null terminators. This allows an attacker to craft malicious input that exceeds the allocated buffer boundaries, potentially overwriting adjacent memory locations with arbitrary data. The flaw directly corresponds to CWE-787, which defines out-of-bounds write vulnerabilities as a critical class of memory safety issues where programs write data beyond the boundaries of allocated memory regions.
The operational impact of this vulnerability extends significantly across network time synchronization infrastructure, as NTP is fundamental to maintaining accurate time across distributed systems. Systems utilizing affected NTP versions could experience denial of service conditions, memory corruption, or potentially remote code execution depending on the specific attack vector and system configuration. The vulnerability affects not only individual hosts but also entire network infrastructures that rely on NTP for time coordination, potentially compromising the integrity of time-sensitive applications and security systems that depend on accurate timekeeping. Attackers could exploit this weakness to disrupt time synchronization services or gain unauthorized access to systems through memory corruption techniques.
Mitigation strategies for CVE-2023-26554 should prioritize immediate patching of affected NTP installations to version 4.2.8p16 or later, which includes the necessary buffer boundary checks and input validation fixes. Organizations should also implement network monitoring to detect anomalous NTP traffic patterns that might indicate exploitation attempts. Additional defensive measures include restricting NTP access to trusted networks, implementing proper input sanitization for time synchronization data, and conducting comprehensive vulnerability assessments of time synchronization infrastructure. From an ATT&CK framework perspective, this vulnerability aligns with techniques related to privilege escalation and denial of service, as it could enable attackers to disrupt critical time services or potentially escalate privileges through memory corruption exploits. System administrators should also consider implementing intrusion detection systems specifically configured to monitor for NTP protocol anomalies and ensure that all network time synchronization services maintain proper access controls and authentication mechanisms.