CVE-2023-26555 in NTP
Summary
by MITRE • 04/12/2023
praecis_parse in ntpd/refclock_palisade.c in NTP 4.2.8p15 has an out-of-bounds write.
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Analysis
by VulDB Data Team • 04/29/2026
The vulnerability identified as CVE-2023-26555 represents a critical out-of-bounds write flaw within the Network Time Protocol implementation, specifically affecting NTP version 4.2.8p15. This issue resides in the praecis_parse function located in the ntpd/refclock_palisade.c source file, which handles parsing of time synchronization data from certain satellite-based time sources. The flaw manifests when the system processes malformed or specially crafted time data from palisade reference clocks, which are typically used in high-precision timing applications. The vulnerability stems from inadequate bounds checking in the parsing logic, allowing an attacker to potentially write data beyond the allocated memory buffer. This type of flaw falls under the CWE-787 weakness category, which specifically addresses out-of-bounds write vulnerabilities that can lead to arbitrary code execution or system compromise. The issue is particularly concerning in network time synchronization environments where NTP servers may be exposed to untrusted network traffic, as it could enable remote attackers to exploit the vulnerability without requiring authentication.
The technical exploitation of this vulnerability requires an attacker to send specifically crafted time data to an NTP server running the affected version and configured to accept palisade reference clock data. When the praecis_parse function processes this malformed input, the lack of proper bounds validation allows memory corruption to occur, potentially leading to denial of service conditions or more severe outcomes depending on the execution environment. The flaw represents a classic buffer overflow scenario where array indices are not properly validated before being used to write data into memory locations beyond the intended buffer boundaries. This vulnerability is particularly dangerous in systems where NTP servers operate in critical infrastructure environments, as it could be leveraged to disrupt time synchronization services that are fundamental to network security operations, cryptographic timestamp validation, and coordinated system operations. The ATT&CK framework categorizes this as a memory corruption vulnerability that could be used for privilege escalation or persistent access within compromised systems.
The operational impact of CVE-2023-26555 extends beyond simple service disruption, as network time synchronization is foundational to many security protocols and system operations. When exploited, this vulnerability could result in widespread time synchronization failures across networks that depend on affected NTP implementations, potentially undermining security measures that rely on accurate timestamps for log analysis, intrusion detection, and cryptographic operations. Organizations running NTP servers in production environments face significant risk, as the vulnerability could be exploited by attackers to create persistent backdoors or to disrupt critical time-sensitive operations. The vulnerability affects systems where palisade reference clocks are configured, which includes various high-precision timing applications used in financial services, telecommunications, and industrial control systems. Mitigation strategies should include immediate patching of affected NTP installations, disabling palisade reference clock configurations where possible, and implementing network segmentation to limit exposure to untrusted time sources. Additionally, organizations should monitor their network traffic for unusual time synchronization patterns that might indicate exploitation attempts, as this vulnerability could be used in conjunction with other attack vectors to establish persistent access to networked systems.