CVE-2000-0545 in mailx
Summary
by MITRE
Buffer overflow in mailx mail command (aka Mail) on Linux systems allows local users to gain privileges via a long -c (carbon copy) parameter.
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Analysis
by VulDB Data Team • 11/17/2024
The vulnerability described in CVE-2000-0545 represents a classic buffer overflow flaw within the mailx mail command implementation on linux systems. This security weakness specifically manifests when processing the -c parameter, which is used to specify carbon copy recipients in email messages. The flaw occurs due to inadequate input validation and bounds checking within the command's argument parsing mechanism, creating an exploitable condition that can be leveraged by local attackers to escalate privileges. The mailx utility, being a widely deployed mail client in unix-like environments, presents a significant attack surface when such vulnerabilities exist in its core functionality.
The technical nature of this buffer overflow stems from the mailx command's failure to properly validate the length of the -c parameter input before copying it into a fixed-size buffer in memory. When a local user provides an excessively long carbon copy argument, the program continues to write data beyond the allocated buffer boundaries, potentially overwriting adjacent memory locations including return addresses, function pointers, or other critical program state information. This memory corruption can be carefully manipulated to redirect program execution flow, allowing an attacker to execute arbitrary code with the privileges of the mailx process, typically running with elevated permissions due to its system integration. The vulnerability is classified as a local privilege escalation vector, as it requires local system access but can potentially provide root-level access depending on how the mailx utility is configured and executed.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it provides attackers with a reliable method to gain unauthorized access to system resources and potentially establish persistent backdoors. Since mailx is commonly used for system administration tasks and may be invoked with elevated privileges, successful exploitation can lead to complete system compromise. The vulnerability affects systems where mailx is installed and used, particularly those running older versions of linux distributions where security patches may not have been applied. Attackers can exploit this by crafting maliciously long -c parameters that trigger the buffer overflow condition, potentially causing program crashes or more dangerously, allowing code execution. The attack vector is particularly concerning because it leverages legitimate system utilities rather than requiring installation of additional malicious software, making detection more difficult.
Mitigation strategies for CVE-2000-0545 should focus on immediate patching of affected mailx implementations and system updates to prevent exploitation. Organizations should ensure that all instances of mailx are updated to versions that properly validate input parameters and implement proper buffer size checking mechanisms. System administrators should also consider implementing input validation at the application level and monitoring for unusual mailx usage patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and represents a classic example of how insufficient input validation can lead to privilege escalation. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques and can be categorized under T1068, which involves exploiting legitimate credentials and system access to gain higher privileges. Additionally, the vulnerability demonstrates the importance of proper memory management in system utilities and the need for robust input sanitization in all command-line interfaces that process user-provided data.