CVE-2016-7431 in M3000
Summary
by MITRE
NTP before 4.2.8p9 allows remote attackers to bypass the origin timestamp protection mechanism via an origin timestamp of zero. NOTE: this vulnerability exists because of a CVE-2015-8138 regression.
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Analysis
by VulDB Data Team • 05/13/2026
The vulnerability identified as CVE-2016-7431 represents a critical security flaw in the Network Time Protocol implementation that affects versions prior to 4.2.8p9. This issue specifically targets the origin timestamp protection mechanism that is fundamental to NTP's security architecture. The vulnerability stems from a regression introduced in CVE-2015-8138, which inadvertently weakened the cryptographic safeguards that protect against malicious time synchronization attacks. The core problem manifests when a remote attacker can manipulate the origin timestamp field within NTP packets to contain a zero value, effectively bypassing the established security controls designed to prevent unauthorized time modifications.
The technical flaw exploits the fundamental trust model of NTP by allowing attackers to submit time synchronization requests with invalid origin timestamps that appear legitimate to the receiving system. When the NTP daemon processes packets with zero origin timestamps, it fails to properly validate the timestamp integrity, creating a window of opportunity for attackers to perform time spoofing attacks. This vulnerability operates at the protocol level within the NTP implementation, specifically affecting the server response handling mechanisms that rely on timestamp verification for authentication purposes. The flaw essentially undermines the cryptographic integrity checks that should prevent malicious actors from manipulating time data across networked systems.
The operational impact of this vulnerability extends beyond simple time synchronization issues, as it can enable attackers to manipulate system clocks across entire networks, potentially compromising security systems that depend on accurate timekeeping. This includes authentication systems, logging mechanisms, and cryptographic operations that rely on time-based validation. Attackers can leverage this vulnerability to conduct time-based attacks such as replay attacks, where old time synchronization data is reused to bypass time-based security controls. The vulnerability particularly affects systems that use NTP for security-critical operations, making it a significant concern for enterprise environments and critical infrastructure deployments.
Mitigation strategies for CVE-2016-7431 require immediate patching of affected NTP implementations to version 4.2.8p9 or later, which includes the necessary fixes to properly validate origin timestamps. Organizations should also implement network-level monitoring to detect anomalous NTP traffic patterns that might indicate exploitation attempts. The fix addresses the regression introduced in CVE-2015-8138 by restoring proper timestamp validation procedures and ensuring that zero values are properly rejected during the NTP packet processing. Security teams should also consider implementing additional controls such as NTP access control lists, rate limiting, and network segmentation to reduce the attack surface. This vulnerability aligns with CWE-284 access control weaknesses and can be categorized under ATT&CK techniques related to time synchronization manipulation and credential access through system time compromise. Organizations should conduct thorough vulnerability assessments to ensure all NTP implementations are updated and properly configured to prevent exploitation of this regression-based security flaw.