CVE-2001-0901 in Hypermail
Summary
by MITRE
Hypermail allows remote attackers to execute arbitrary commands on a server supporting SSI via an attachment with a .shtml extension, which is archived on the server and can then be executed by requesting the URL for the attachment.
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Analysis
by VulDB Data Team • 04/10/2019
The vulnerability described in CVE-2001-0901 represents a critical security flaw in the Hypermail mailing list software that enables remote command execution through server-side includes. This vulnerability specifically targets servers that support server-side inclusion mechanisms and have Hypermail configured to process attachments with .shtml extensions. The flaw arises from inadequate input validation and improper handling of file extensions within the archive processing functionality, creating a pathway for malicious actors to inject and execute arbitrary commands on the affected server.
The technical implementation of this vulnerability leverages the server-side includes feature that allows HTML files to contain executable code segments. When Hypermail processes an attachment with a .shtml extension, it fails to properly sanitize or validate the content, treating the file as executable rather than a simple attachment. The server then archives this file and makes it accessible through URL requests, allowing attackers to trigger the execution of malicious code simply by accessing the archived attachment. This represents a classic server-side include vulnerability where the web application's processing logic does not properly distinguish between legitimate server-side include directives and potentially malicious code embedded within uploaded files.
The operational impact of this vulnerability extends far beyond simple data compromise, as it provides attackers with complete control over the affected server. Successful exploitation allows adversaries to execute arbitrary commands with the privileges of the web server process, potentially leading to full system compromise, data exfiltration, or further lateral movement within the network. The vulnerability is particularly dangerous because it requires minimal user interaction beyond simply uploading a malicious attachment, making it an attractive target for automated exploitation. Organizations running Hypermail on servers with SSI support face significant risk, as the vulnerability can be exploited without requiring authentication or specialized knowledge of the target system.
Security mitigations for this vulnerability must address both the immediate exposure and underlying architectural flaws in the Hypermail implementation. The most effective immediate solution involves disabling SSI processing for uploaded attachments or implementing strict file extension validation that prevents .shtml files from being processed as executable content. Organizations should also implement proper input sanitization mechanisms that strip or escape any server-side include directives from uploaded files before archiving them. Additionally, network segmentation and access controls should be implemented to limit the potential impact of successful exploitation, while regular security audits should verify that no .shtml files are being processed as executable content within the Hypermail environment. This vulnerability aligns with CWE-94, which describes improper control of generation of code, and represents a specific instance of the broader category of server-side include injection attacks that fall under ATT&CK technique T1059.007 for command and script injection.