CVE-2015-7701 in ntpd
Summary
by MITRE
Memory leak in the CRYPTO_ASSOC function in ntpd in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to cause a denial of service (memory consumption).
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Analysis
by VulDB Data Team • 06/25/2022
The vulnerability identified as CVE-2015-7701 represents a critical memory leak flaw within the Network Time Protocol daemon implementation that affects multiple versions of the ntpd service. This issue resides in the CRYPTO_ASSOC function which handles cryptographic associations within the NTP protocol stack, making it particularly dangerous as it can be exploited remotely without authentication. The vulnerability specifically impacts NTP versions 4.2.x prior to 4.2.8p4 and 4.3.x prior to 4.3.77, indicating a widespread exposure across numerous production systems that rely on NTP for time synchronization. The flaw operates by failing to properly release allocated memory resources when processing cryptographic associations, leading to gradual memory exhaustion over time.
The technical mechanism behind this vulnerability involves improper memory management within the cryptographic association handling code path of ntpd. When the CRYPTO_ASSOC function processes incoming network packets containing cryptographic parameters, it allocates memory for association structures but fails to consistently free this memory upon completion of operations. This memory leak occurs repeatedly with each processed packet, allowing attackers to send specially crafted NTP packets that trigger the vulnerable code path. The vulnerability manifests as a progressive increase in memory consumption on the affected NTP server, eventually leading to system instability and complete denial of service. According to CWE classification, this represents a CWE-401: Improper Release of Memory Before Removing Last Reference, which is a fundamental memory management error that has been consistently identified as a critical weakness in software systems.
The operational impact of CVE-2015-7701 extends beyond simple resource exhaustion, creating a significant risk to network infrastructure reliability and availability. Organizations relying on NTP services for time synchronization across critical systems face potential cascading failures when the memory leak reaches critical thresholds. The vulnerability's remote exploitability means that attackers can initiate the attack from any network location without requiring physical access or authentication credentials, making it particularly dangerous in enterprise environments where NTP servers often serve as foundational infrastructure components. This weakness directly maps to ATT&CK technique T1499.001 which involves resource exhaustion attacks through manipulation of network services, and can be leveraged as part of broader denial of service campaigns targeting network infrastructure. The vulnerability's exploitation can cause systems to become unresponsive, potentially leading to service interruptions that affect critical business operations and network time synchronization across multiple dependent systems.
Mitigation strategies for CVE-2015-7701 primarily focus on immediate patch deployment and system hardening measures. Organizations should prioritize upgrading to NTP versions 4.2.8p4 or later for 4.2.x releases, and 4.3.77 or later for 4.3.x releases, as these versions contain the necessary memory management fixes. Network administrators should implement monitoring solutions to track memory consumption patterns on NTP servers and establish automated alerting for unusual memory usage trends. Additionally, network segmentation and access controls should be implemented to limit exposure of NTP servers to untrusted networks, reducing the attack surface. The vulnerability also underscores the importance of regular security assessments and vulnerability management programs that can identify and remediate similar memory management issues across network infrastructure components. Implementing proper memory leak detection tools and conducting regular code reviews focused on resource management practices can help prevent similar issues from emerging in other software components.