CVE-2018-7184 in ntp
Summary
by MITRE
ntpd in ntp 4.2.8p4 before 4.2.8p11 drops bad packets before updating the "received" timestamp, which allows remote attackers to cause a denial of service (disruption) by sending a packet with a zero-origin timestamp causing the association to reset and setting the contents of the packet as the most recent timestamp. This issue is a result of an incomplete fix for CVE-2015-7704.
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Analysis
by VulDB Data Team • 01/15/2025
The vulnerability described in CVE-2018-7184 affects the Network Time Protocol daemon (ntpd) in ntp versions prior to 4.2.8p11, specifically exposing a denial of service weakness that stems from an incomplete remediation of a previous security issue. This flaw manifests when ntpd processes packets containing zero-origin timestamps, creating a scenario where the system drops these packets before updating the "received" timestamp, thereby enabling remote attackers to disrupt time synchronization services. The root cause lies in the improper handling of timestamp validation within the protocol implementation, where the system fails to properly account for edge cases in timestamp processing that were not fully addressed in the initial fix for CVE-2015-7704. This vulnerability operates at the network protocol level and directly impacts the availability of time synchronization services across affected systems.
The technical mechanism behind this vulnerability involves the ntpd daemon's handling of packet timestamps during association management. When a packet with a zero-origin timestamp is received, the system's flawed logic causes it to drop the packet before updating the timestamp tracking mechanism. This premature packet dropping triggers an association reset, which subsequently causes the system to treat the packet contents as the most recent timestamp value. The flaw creates a recursive condition where malformed packets can repeatedly trigger the reset mechanism, leading to sustained disruption of time synchronization services. This behavior represents a classic denial of service vector that exploits the protocol's internal state management rather than external network conditions. The vulnerability aligns with CWE-400, which categorizes improper handling of resource exhaustion conditions, and demonstrates how incomplete security patches can create new attack surfaces. From an operational perspective, this vulnerability affects systems that rely on ntp for time synchronization, including network infrastructure devices, servers, and critical applications that depend on accurate timekeeping.
The operational impact of CVE-2018-7184 extends beyond simple service disruption to potentially compromise the reliability of time-sensitive operations across networked environments. When exploited, this vulnerability can cause cascading effects where multiple systems dependent on synchronized time fail to maintain proper coordination, affecting authentication systems, log correlation, and security event tracking. The attack requires minimal resources from the attacker, making it particularly dangerous as it can be triggered remotely with simple packet crafting techniques. Network administrators may observe intermittent service disruptions or complete loss of time synchronization capabilities, which can severely impact system integrity and security posture. The vulnerability's persistence stems from its location within the core protocol processing logic, meaning that even systems with proper network segmentation may experience disruption if they rely on ntp for time services. This weakness also aligns with ATT&CK technique T1499.001, which covers network denial of service attacks, and represents a failure in protocol robustness that affects the fundamental availability of time synchronization services. Organizations may find that their existing security monitoring systems struggle to detect this attack pattern since it operates within legitimate network protocol behavior, making it particularly challenging to identify and mitigate without specific awareness of the vulnerability. The remediation requires updating to ntp version 4.2.8p11 or later, which implements a complete fix for the timestamp handling logic that prevents the association reset condition while maintaining proper protocol compliance.