CVE-2002-0601 in RealSecure Network Sensor
Summary
by MITRE
ISS RealSecure Network Sensor 5.x through 6.5 allows remote attackers to cause a denial of service (crash) via malformed DHCP packets that cause RealSecure to dereference a null pointer.
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Analysis
by VulDB Data Team • 04/12/2019
The vulnerability identified as CVE-2002-0601 affects ISS RealSecure Network Sensor versions 5.x through 6.5, representing a critical denial of service weakness that can be exploited remotely by attackers. This flaw manifests through the processing of malformed DHCP packets, which triggers a null pointer dereference condition within the RealSecure network monitoring system. The vulnerability stems from inadequate input validation mechanisms within the DHCP packet handling code, where the software fails to properly validate the structure and content of received DHCP messages before attempting to process them. This particular issue falls under the CWE-476 category of NULL Pointer Dereference, which represents a fundamental programming error where software attempts to access memory through a null pointer reference, leading to system crashes or unexpected behavior.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged by remote attackers to systematically crash the RealSecure network sensor devices. When malformed DHCP packets are transmitted to the vulnerable system, the network sensor's DHCP processing module encounters a null pointer dereference condition that results in an immediate system crash and subsequent denial of service. This makes the affected network monitoring infrastructure completely unavailable for its intended security functions, potentially leaving networks exposed to other threats during the downtime period. The vulnerability is particularly concerning because DHCP is a fundamental protocol used by network devices to obtain IP configuration information, making it an attractive target for attackers seeking to disrupt network operations.
From a cybersecurity perspective, this vulnerability demonstrates the importance of robust input validation and error handling in network security appliances. The attack vector relies on the attacker sending specially crafted DHCP packets that exploit the lack of proper bounds checking and null pointer validation within the RealSecure software. The attack requires no authentication and can be executed from any location on the network, making it particularly dangerous for network security devices that are designed to be accessible from multiple network segments. This vulnerability aligns with ATT&CK technique T1499.004 for network denial of service attacks, where adversaries leverage protocol-level vulnerabilities to disrupt network services.
The mitigation strategies for this vulnerability involve applying the vendor-provided patches and updates that address the null pointer dereference issue in the DHCP packet processing code. Network administrators should prioritize updating their RealSecure sensors to versions that contain proper input validation and error handling mechanisms for DHCP packets. Additionally, implementing network segmentation and access control measures can help reduce the attack surface by limiting the network segments where DHCP services are accessible. The vulnerability also underscores the importance of regular security assessments and penetration testing to identify similar flaws in network security infrastructure, particularly in legacy systems that may not receive regular security updates. Organizations should also consider implementing network monitoring solutions that can detect and alert on abnormal DHCP traffic patterns that might indicate exploitation attempts.