CVE-1999-0941 in Mail Client
Summary
by MITRE
Mutt mail client allows a remote attacker to execute commands via shell metacharacters.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 04/17/2026
The vulnerability described in CVE-1999-0941 represents a critical command injection flaw within the Mutt mail client, a widely used open-source email application that has been a cornerstone of email communication in Unix-like environments for decades. This vulnerability specifically affects the handling of shell metacharacters within the application's command processing mechanisms, creating a pathway for remote attackers to execute arbitrary commands on systems where Mutt is installed. The flaw stems from insufficient input validation and sanitization of user-supplied data that flows into shell execution contexts, making it particularly dangerous as it can be exploited over network connections without requiring local system access.
The technical nature of this vulnerability aligns with CWE-78, which describes improper neutralization of special elements used in shell commands, and represents a classic example of a command injection attack vector. When Mutt processes certain email headers or attachments containing shell metacharacters such as semicolons, ampersands, or backticks, the application fails to properly escape or sanitize these characters before passing them to underlying shell commands. This allows an attacker who can influence the content of email messages to inject malicious shell commands that get executed with the privileges of the user running Mutt. The vulnerability is particularly concerning because email clients like Mutt are often used in environments where users may receive untrusted email from external sources, making the attack surface broad and the exploitation potential high.
The operational impact of this vulnerability extends far beyond simple command execution, as it can enable full system compromise when Mutt is run with elevated privileges or when users interact with malicious emails containing crafted payloads. Attackers can leverage this vulnerability to gain unauthorized access to email servers, extract sensitive information from user accounts, establish persistent backdoors, or use the compromised system as a launch point for further attacks within a network. The vulnerability affects not only individual users but also organizations that rely on Mutt for email processing, as it can be exploited through various attack vectors including phishing emails, compromised email servers, or even through malicious attachments that trigger shell command execution when processed by the application. This type of vulnerability is particularly dangerous in enterprise environments where email systems are critical infrastructure components and where users may inadvertently execute malicious commands simply by viewing or interacting with email content.
Mitigation strategies for CVE-1999-0941 require immediate action including applying security patches from the Mutt development team, implementing strict input validation mechanisms, and deploying network-based security controls to monitor and filter potentially malicious email content. Organizations should consider implementing email security gateways that can detect and block suspicious shell metacharacters in email headers and attachments, while also ensuring that Mutt is configured to run with minimal privileges and that users are educated about the risks of opening untrusted email content. The vulnerability demonstrates the importance of following secure coding practices such as those outlined in the OWASP Secure Coding Guidelines and aligns with ATT&CK technique T1059.007 for command and scripting interpreter, emphasizing the need for proper input sanitization and the principle of least privilege in application design. System administrators should also implement monitoring and logging mechanisms to detect potential exploitation attempts and establish incident response procedures to quickly address any successful attacks. Given the age of this vulnerability and its continued relevance in modern security assessments, organizations must ensure that their email security infrastructure remains robust against similar command injection threats that may exist in other email clients or email processing systems.