CVE-2023-26553 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 copying the trailing number.
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Analysis
by VulDB Data Team • 04/29/2026
The vulnerability identified as CVE-2023-26553 resides within the Network Time Protocol implementation in the libntp library version 4.2.8p15. This issue manifests in the mstolfp function located in the mstolfp.c source file, where a critical out-of-bounds write condition occurs during the processing of trailing numeric values. The flaw represents a classic buffer management error that can potentially lead to system compromise when exploited by malicious actors.
The technical implementation of this vulnerability stems from improper bounds checking during string parsing operations within the NTP time synchronization protocol. When the mstolfp function processes numeric data from time-related configuration parameters or network packets, it fails to adequately validate the length of trailing numeric sequences before performing memory copy operations. This oversight creates a scenario where an attacker can craft malicious input that exceeds the allocated buffer boundaries, resulting in memory corruption that may allow arbitrary code execution or system instability.
From an operational perspective, this vulnerability poses significant risks to network infrastructure relying on NTP services for time synchronization. The out-of-bounds write condition can be triggered through malformed time-related data packets or configuration inputs, potentially affecting servers, routers, and network devices that utilize the affected libntp library. The impact extends beyond simple service disruption to potential privilege escalation and remote code execution depending on the execution context of the vulnerable process.
This vulnerability aligns with CWE-787, which specifically addresses out-of-bounds write conditions in software implementations. The flaw demonstrates characteristics consistent with the ATT&CK technique T1059.007 for command and scripting interpreter, as exploitation may involve crafting malicious inputs that trigger the buffer overflow during normal NTP operations. The vulnerability also relates to T1566.001 for spearphishing with attachment, where attackers might deliver malicious NTP configurations or network packets designed to exploit this condition.
Mitigation strategies should prioritize immediate patching of the affected libntp library to version 4.2.8p16 or later, which includes the necessary bounds checking fixes. Network administrators should implement monitoring solutions to detect unusual NTP traffic patterns that might indicate exploitation attempts. Additional defensive measures include restricting NTP traffic to trusted sources, implementing proper input validation for time-related configuration parameters, and maintaining regular security updates for all network time synchronization services. The vulnerability underscores the importance of rigorous input validation and bounds checking in protocol implementations, particularly those handling time-sensitive network communications where reliability and security are paramount.