CVE-2001-0035 in Kerberos
Summary
by MITRE
Buffer overflow in the kdc_reply_cipher function in KTH Kerberos IV allows remote attackers to cause a denial of service and possibly execute arbitrary commands via a long authentication request.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 06/25/2021
The vulnerability identified as CVE-2001-0035 represents a critical buffer overflow flaw within the KTH Kerberos IV implementation that specifically affects the kdc_reply_cipher function. This issue stems from inadequate input validation mechanisms that fail to properly handle authentication requests exceeding predetermined buffer limits. The vulnerability exists in the Kerberos authentication system's key distribution center component, which serves as a central authority for issuing and managing cryptographic keys within the Kerberos framework. The buffer overflow condition occurs when the system processes authentication requests that contain excessively long cipher data, causing memory corruption that can lead to unpredictable system behavior and potential exploitation by malicious actors. This flaw directly impacts the integrity and availability of Kerberos authentication services, which were widely deployed across enterprise networks and government systems during the late 1990s and early 2000s.
The technical exploitation of this vulnerability leverages the fundamental weakness in memory management within the kdc_reply_cipher function where input data is copied into fixed-size buffers without proper bounds checking. When an attacker crafts a malicious authentication request containing oversized cipher data, the system's failure to validate input length results in memory overwrite conditions that can corrupt adjacent memory regions. This memory corruption can manifest in several ways including program crashes, stack corruption, or potentially more severe outcomes where the attacker might be able to manipulate execution flow to execute arbitrary code. The vulnerability falls under CWE-121, which specifically addresses stack-based buffer overflow conditions, and demonstrates how improper input validation in cryptographic systems can create significant security risks. The attack surface is particularly concerning because Kerberos IV was designed to provide secure authentication services, making this vulnerability especially dangerous when attackers can exploit it to either deny legitimate authentication services or potentially gain unauthorized access to systems.
The operational impact of CVE-2001-0035 extends beyond simple denial of service scenarios to encompass potential system compromise and widespread authentication failures across networks relying on KTH Kerberos IV implementations. Organizations using vulnerable Kerberos systems would experience authentication service disruptions that could cascade throughout their network infrastructure, affecting multiple services that depend on Kerberos for authentication. The vulnerability's potential for arbitrary code execution places organizations at risk of full system compromise, particularly when the KDC service runs with elevated privileges. This threat model aligns with ATT&CK technique T1078 which covers valid accounts and T1210 which addresses exploitation of remote services. The widespread deployment of KTH Kerberos IV in enterprise environments meant that a single vulnerable implementation could affect numerous systems and users, creating a significant risk for organizations that had not yet migrated to more secure Kerberos implementations or had not applied patches to their systems.
Mitigation strategies for this vulnerability require immediate patch application from vendors and system administrators to address the buffer overflow in the kdc_reply_cipher function. Organizations should implement input validation measures to prevent oversized authentication requests from reaching vulnerable systems, though this approach provides only partial protection given the nature of the underlying flaw. Network segmentation and access controls should be enhanced to limit exposure of vulnerable Kerberos services to untrusted networks and users. System administrators should monitor authentication logs for unusual patterns that might indicate exploitation attempts, particularly focusing on authentication requests with malformed cipher data. The most effective long-term solution involves migrating to updated Kerberos implementations that have addressed these buffer overflow vulnerabilities and incorporate proper input validation and memory management practices. Security monitoring systems should be configured to detect and alert on potential exploitation attempts targeting this specific vulnerability, and organizations should conduct comprehensive vulnerability assessments to identify all systems running affected KTH Kerberos IV implementations. Regular security updates and proper configuration management practices are essential to prevent similar vulnerabilities from being exploited in modern systems, particularly given the historical prevalence of such buffer overflow issues in network services.