CVE-2006-3084 in Kerberos
Summary
by MITRE
The (1) ftpd and (2) ksu programs in (a) MIT Kerberos 5 (krb5) up to 1.5, and 1.4.x before 1.4.4, and (b) Heimdal 0.7.2 and earlier, do not check return codes for setuid calls, which might allow local users to gain privileges by causing setuid to fail to drop privileges. NOTE: as of 20060808, it is not known whether an exploitable attack scenario exists for these issues.
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Analysis
by VulDB Data Team • 01/20/2025
The vulnerability described in CVE-2006-3084 represents a critical privilege escalation flaw affecting authentication and authorization systems within Kerberos implementations. This issue impacts both MIT Kerberos 5 versions up to 1.5 and 1.4.x before 1.4.4, as well as Heimdal 0.7.2 and earlier versions. The core problem lies in the improper handling of setuid system calls within two specific programs: ftpd and ksu. These programs are designed to operate with elevated privileges to perform administrative functions, but the flawed implementation fails to properly verify the success of setuid operations that should drop these elevated privileges back to regular user permissions.
The technical flaw stems from the absence of return code validation for setuid calls in the affected software components. When a program executes a setuid system call, it should verify that the operation completed successfully before proceeding with its normal execution flow. In this case, if the setuid call fails for any reason - such as resource constraints, permission issues, or system limitations - the program continues execution with elevated privileges instead of properly dropping them. This creates a persistent security boundary violation where local users can potentially maintain administrative access longer than intended. The vulnerability operates under CWE-252, which categorizes improper checking of return values, specifically in the context of privilege management operations.
The operational impact of this vulnerability is significant for systems relying on these Kerberos implementations for network authentication and authorization. Local attackers who can execute code on affected systems gain the ability to maintain elevated privileges beyond what is normally permitted, potentially leading to complete system compromise. The attack vector is particularly concerning because it requires only local access, making it difficult to detect and prevent through network-based security measures. The vulnerability essentially creates a backdoor privilege escalation mechanism that could be exploited by malicious users or compromised processes to gain unauthorized administrative access to systems using affected Kerberos implementations.
Security professionals should prioritize patching affected systems by upgrading to versions that properly validate setuid return codes, typically those released after the vulnerability was identified. The recommended mitigation strategy involves ensuring that all setuid operations in these programs include proper error checking and that failed privilege drops result in program termination rather than continued execution with elevated privileges. Additionally, system administrators should implement monitoring for unusual privilege escalation activities and consider implementing additional security controls such as mandatory access controls or privilege separation mechanisms to limit the potential impact of such vulnerabilities. Organizations should also conduct thorough vulnerability assessments to identify any other programs within their environment that might exhibit similar privilege management flaws, as this represents a common pattern in security-critical system components. The issue aligns with ATT&CK technique T1068, which covers privilege escalation through local exploitation of system vulnerabilities, making it a critical concern for enterprise security teams implementing robust access control policies.