CVE-2014-9751 in ntp
Summary
by MITRE
The read_network_packet function in ntp_io.c in ntpd in NTP 4.x before 4.2.8p1 on Linux and OS X does not properly determine whether a source IP address is an IPv6 loopback address, which makes it easier for remote attackers to spoof restricted packets, and read or write to the runtime state, by leveraging the ability to reach the ntpd machine's network interface with a packet from the ::1 address.
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Analysis
by VulDB Data Team • 06/20/2022
The vulnerability described in CVE-2014-9751 represents a critical security flaw in the Network Time Protocol daemon implementation that affects NTP versions prior to 4.2.8p1 on Linux and macOS operating systems. This issue stems from improper handling of IPv6 loopback address validation within the network packet processing logic of ntpd, specifically within the read_network_packet function located in ntp_io.c. The flaw creates a significant pathway for remote attackers to bypass security restrictions that are typically enforced for loopback traffic, which should normally be restricted to local system access only.
The technical root cause of this vulnerability lies in the insufficient validation of source IP addresses when processing network packets. The ntpd implementation fails to correctly identify when a packet originates from the IPv6 loopback address ::1, which should be treated as a local system address and subjected to stricter security controls. This misidentification allows attackers to craft packets that appear to originate from the loopback interface while actually coming from remote locations, effectively circumventing the intended security boundaries that protect the NTP daemon's runtime state. The vulnerability specifically impacts the network I/O handling mechanism where the daemon processes incoming packets, creating a scenario where remote adversaries can manipulate the daemon's behavior through crafted network traffic.
The operational impact of this vulnerability is substantial as it enables remote attackers to perform unauthorized operations on the NTP daemon's runtime state. An attacker who successfully exploits this vulnerability can potentially read sensitive information from the daemon's memory, write to its runtime configuration, or manipulate time synchronization data in ways that could compromise the integrity of time-sensitive applications and services. This capability extends beyond simple information disclosure to potentially allow for more sophisticated attacks including time-based privilege escalation or disruption of critical time synchronization services that many enterprise systems depend upon for security operations.
This vulnerability maps to CWE-20, "Improper Input Validation," and aligns with ATT&CK technique T1071.004, "Application Layer Protocol: DNS," though it more directly relates to network protocol handling and privilege escalation through malformed packet processing. The attack vector leverages the fact that IPv6 loopback addresses are typically restricted to local system access, but the flawed implementation allows remote access to these restricted pathways. Organizations running affected NTP versions are particularly vulnerable since the NTP daemon often runs with elevated privileges to manage system time synchronization, making successful exploitation potentially devastating for system security and integrity. The vulnerability demonstrates a classic case of insufficient network address validation that creates an unexpected attack surface for remote adversaries.
Mitigation strategies should prioritize immediate patching of affected NTP installations to version 4.2.8p1 or later, which contains the necessary fixes for proper IPv6 loopback address validation. System administrators should also implement network-level restrictions to prevent unauthorized access to NTP ports and consider deploying firewalls or network access control lists that specifically block traffic from unexpected sources. Additionally, monitoring for unusual patterns in NTP packet processing and implementing intrusion detection systems that can identify potential exploitation attempts will help in detecting and responding to attacks targeting this vulnerability. The fix implemented in the patched versions ensures that the read_network_packet function correctly identifies and handles IPv6 loopback addresses, thereby restoring the intended security boundaries that protect the NTP daemon from unauthorized remote access.