CVE-2004-2771 in mailx
Summary
by MITRE
The expand function in fio.c in Heirloom mailx 12.5 and earlier and BSD mailx 8.1.2 and earlier allows remote attackers to execute arbitrary commands via shell metacharacters in an email address.
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Analysis
by VulDB Data Team • 04/09/2022
The vulnerability described in CVE-2004-2771 represents a critical command injection flaw affecting email client software, specifically within the expand function of fio.c in Heirloom mailx versions 12.5 and earlier, as well as BSD mailx versions 8.1.2 and earlier. This security weakness arises from insufficient input validation and sanitization when processing email addresses, creating an environment where malicious actors can exploit shell metacharacters to execute arbitrary commands on the target system. The flaw demonstrates a classic buffer overflow and command injection pattern that has been documented in numerous security advisories over the years.
The technical implementation of this vulnerability stems from the improper handling of email address parsing within the mailx application's file input/output operations. When the expand function processes email addresses, it fails to adequately sanitize user-supplied input, allowing shell metacharacters such as semicolons, pipes, and backticks to be interpreted as command delimiters or execution operators. This design flaw enables attackers to craft malicious email addresses that, when processed by the vulnerable software, result in unintended command execution. The vulnerability operates at the application layer and can be exploited remotely without requiring authentication, making it particularly dangerous in networked environments where email processing occurs automatically.
From an operational perspective, this vulnerability presents significant risks to system integrity and confidentiality. Attackers can leverage this flaw to execute commands with the privileges of the mailx process, potentially leading to complete system compromise, data exfiltration, or lateral movement within a network. The impact extends beyond simple command execution, as successful exploitation can result in persistent backdoor installation, privilege escalation, and denial of service conditions. Organizations relying on these vulnerable email clients face potential exposure to automated attacks and targeted exploitation attempts, particularly in environments where email processing is automated or where users receive emails from untrusted sources.
Mitigation strategies for CVE-2004-2771 should focus on immediate software updates and patches to address the underlying command injection vulnerability. System administrators must prioritize updating to patched versions of Heirloom mailx and BSD mailx, as these releases contain proper input validation and sanitization mechanisms. Additionally, implementing network-level restrictions such as email filtering and content inspection can provide defense-in-depth measures to prevent malicious email addresses from reaching vulnerable systems. The vulnerability aligns with CWE-78, which specifically addresses improper neutralization of special elements used in OS commands, and maps to ATT&CK technique T1059.007 for Command and Scripting Interpreter: Unix Shell, highlighting the need for comprehensive security measures including input validation, privilege separation, and regular security assessments to prevent exploitation of similar vulnerabilities in email processing systems.