CVE-2019-6442 in NTPsec
Summary
by MITRE
An issue was discovered in NTPsec before 1.1.3. An authenticated attacker can write one byte out of bounds in ntpd via a malformed config request, related to config_remotely in ntp_config.c, yyparse in ntp_parser.tab.c, and yyerror in ntp_parser.y.
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Analysis
by VulDB Data Team • 12/22/2024
The vulnerability identified as CVE-2019-6442 represents a critical out-of-bounds write flaw within the NTPsec network time synchronization daemon version 1.1.2 and earlier. This issue affects the ntpd service which is widely deployed across enterprise networks for maintaining precise time synchronization. The vulnerability stems from insufficient input validation during configuration request processing, specifically within the remote configuration handling mechanisms that allow authorized users to modify daemon settings. The flaw manifests when an authenticated attacker submits a malformed configuration request that triggers an improper memory access pattern during parsing operations. The vulnerability is particularly concerning because it occurs in the configuration parsing subsystem where legitimate administrative functions are processed, making it difficult to distinguish between normal operational traffic and malicious attempts to exploit the memory corruption.
The technical implementation of this vulnerability resides in multiple interconnected components within the NTPsec codebase. The primary flaw occurs in the config_remotely function within ntp_config.c where configuration data is processed for remote modifications. Additionally, the yyparse function in ntp_parser.tab.c and yyerror function in ntp_parser.y demonstrate memory boundary violations during parsing of malformed configuration inputs. These functions utilize a parser generated by yacc/bison tools and demonstrate a classic buffer overflow condition where a single byte write operation extends beyond allocated memory boundaries. The vulnerability is classified under CWE-787 as an out-of-bounds write, specifically a heap-based buffer overflow that can be triggered through authenticated network access. This type of vulnerability allows for arbitrary memory corruption that can potentially lead to privilege escalation or denial of service conditions.
The operational impact of CVE-2019-6442 extends beyond simple service disruption to encompass potential system compromise and network stability threats. When exploited, the out-of-bounds write can corrupt critical memory segments including function pointers, return addresses, or configuration variables that control daemon behavior. This memory corruption can result in unpredictable program execution paths, leading to crashes that affect time synchronization across the network or potentially allow attackers to execute arbitrary code with the privileges of the ntpd process. The authenticated nature of the attack means that an attacker must first establish valid credentials to access the NTP daemon's configuration interface, but once achieved, the impact can be severe given that NTP daemons typically run with elevated privileges. The vulnerability affects organizations that rely on NTPsec for time synchronization, particularly those with multiple time servers or complex network topologies where time accuracy is critical for security operations and compliance requirements.
Organizations should immediately implement mitigations including updating to NTPsec version 1.1.3 or later where the vulnerability has been patched through proper input validation and memory boundary checks. The patch addresses the issue by implementing proper bounds checking in the parser functions and ensuring that configuration data cannot exceed allocated buffer sizes during processing. Network segmentation and access controls should be reinforced to limit who can submit configuration requests to NTP daemons, reducing the attack surface for authenticated exploits. Security monitoring should be enhanced to detect unusual configuration request patterns that might indicate exploitation attempts, particularly focusing on malformed requests that could trigger the parser functions. System administrators should also consider implementing intrusion detection systems that can monitor for memory corruption patterns and anomalous behavior in time synchronization services. The vulnerability demonstrates the importance of proper input validation in network services and aligns with ATT&CK technique T1059.001 for command and scripting interpreter usage, as exploitation could potentially lead to command execution through memory corruption. Organizations should also review their patch management processes to ensure timely application of security updates to critical infrastructure services like network time protocol daemons.