CVE-2006-4520 in eDirectory
Summary
by MITRE
ncp in Novell eDirectory before 8.7.3 SP9, and 8.8.x before 8.8.1 FTF2, does not properly handle NCP fragments with a negative length, which allows remote attackers to cause a denial of service (daemon crash) when the heap is written to a log file.
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Analysis
by VulDB Data Team • 03/13/2015
The vulnerability identified as CVE-2006-4520 affects the NetWare Core Protocol (NCP) implementation within Novell eDirectory software, specifically impacting versions prior to 8.7.3 SP9 and 8.8.x prior to 8.8.1 FTF2. This issue represents a classic buffer over-read condition that occurs when the NCP daemon processes malformed fragment packets containing negative length values. The flaw exists in how the system handles memory allocation and data processing for network fragments, creating a scenario where malicious input can trigger unexpected behavior in the protocol handler.
The technical implementation of this vulnerability stems from inadequate input validation within the NCP fragment processing logic. When the NCP daemon encounters a fragment with a negative length value, it fails to properly validate this input before attempting to allocate memory or process the data. This improper handling causes the system to attempt to write to heap memory locations that are either invalid or improperly allocated, leading to memory corruption. The vulnerability is classified under CWE-129 as an Improper Validation of Array Index, specifically manifesting as an insufficient boundary check on fragment length parameters. The flaw operates at the protocol level where network packets are parsed and processed, making it particularly dangerous as it can be exploited remotely without authentication requirements.
The operational impact of this vulnerability extends beyond simple denial of service, as it can result in complete daemon crashes that disrupt directory services for entire network domains. When exploited, the negative length fragments cause the NCP daemon to enter an undefined state where it attempts to write to invalid memory locations, leading to segmentation faults or heap corruption that terminates the process. This type of remote code execution in the form of denial of service can severely impact enterprise environments that rely heavily on Novell eDirectory for authentication, directory services, and network resource management. The attack vector is particularly concerning as it requires no special privileges and can be executed from any network location capable of sending malformed packets to the target system.
Mitigation strategies for this vulnerability should focus on immediate patch deployment as the primary defense mechanism, with the recommended version updates being Novell eDirectory 8.7.3 SP9 or 8.8.1 FTF2. Network administrators should implement defensive measures including firewall rules that filter out malformed NCP packets and monitor for unusual traffic patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation and memory management in network protocol implementations, aligning with ATT&CK technique T1499.004 for Network Denial of Service. Organizations should also consider implementing intrusion detection systems that can identify and alert on malformed NCP fragment patterns, as well as establishing robust logging and monitoring procedures to detect early signs of exploitation attempts. Additionally, network segmentation strategies can limit the potential impact of successful exploitation by isolating critical directory services from less secure network segments.