CVE-2000-0170 in Linux
Summary
by MITRE
Buffer overflow in the man program in Linux allows local users to gain privileges via the MANPAGER environmental variable.
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Analysis
by VulDB Data Team • 12/01/2024
The vulnerability identified as CVE-2000-0170 represents a critical buffer overflow flaw within the man program on Linux systems, specifically affecting the handling of the MANPAGER environment variable. This issue resides in the core documentation viewer utility that is fundamental to Unix-like operating systems, making it a significant security concern that could be exploited by local attackers to escalate privileges. The man program serves as the primary interface for accessing manual pages and system documentation, and its vulnerability creates a pathway for unauthorized privilege escalation that directly impacts system integrity and security posture.
The technical implementation of this vulnerability stems from improper input validation within the man program's processing of the MANPAGER environment variable. When a user sets this environment variable to specify an alternative pager for displaying manual pages, the program fails to properly bounds-check the input string before copying it into a fixed-size buffer. This classic buffer overflow condition occurs because the program assumes the MANPAGER value will fit within predetermined memory limits without performing adequate length verification. The flaw is categorized as a CWE-121 stack-based buffer overflow, where insufficient bounds checking allows an attacker to overwrite adjacent memory locations, potentially including return addresses and control data. This vulnerability specifically aligns with ATT&CK technique T1068 which involves privilege escalation through local exploitation of software vulnerabilities.
The operational impact of this vulnerability extends beyond simple local privilege escalation, as it provides attackers with the capability to execute arbitrary code with elevated privileges. When exploited, the buffer overflow can overwrite the program's return address on the stack, allowing an attacker to redirect execution flow to malicious code. This creates a persistent security risk that can be leveraged to gain root access, modify system files, install backdoors, or establish persistent access to the compromised system. The vulnerability is particularly dangerous because it requires no network connectivity and can be exploited through local system access, making it a preferred target for attackers who have already gained initial access to a system. The attack vector involves crafting a specially crafted MANPAGER environment variable that exceeds the buffer capacity, leading to memory corruption that can be manipulated to achieve code execution.
Mitigation strategies for CVE-2000-0170 should focus on immediate patching of the affected man program versions, as the original vulnerability was resolved through proper bounds checking and input validation implementations. System administrators should ensure that all Linux distributions are updated with the latest security patches from their respective vendors, as this vulnerability was addressed in subsequent releases of the man-db package. Additionally, implementing proper environment variable sanitization and employing secure coding practices during software development can prevent similar issues from occurring in other applications. The vulnerability serves as a reminder of the importance of input validation and memory safety practices in system utilities, particularly those that may be invoked with elevated privileges. Organizations should also consider implementing runtime protections such as stack canaries, address space layout randomization, and non-executable stack protections to mitigate the impact of similar buffer overflow vulnerabilities that may exist in other system components.