CVE-2004-0520 in SquirrelMail
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in mime.php for SquirrelMail before 1.4.3 allows remote attackers to insert arbitrary HTML and script via the content-type mail header, as demonstrated using read_body.php.
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Analysis
by VulDB Data Team • 01/01/2025
The vulnerability described in CVE-2004-0520 represents a classic cross-site scripting flaw within the SquirrelMail webmail application ecosystem. This issue affects versions prior to 1.4.3 and specifically targets the mime.php component that processes email content types. The vulnerability stems from insufficient input validation and output sanitization mechanisms within the email parsing logic, creating an exploitable condition where malicious actors can inject arbitrary HTML and script code through email headers. The attack vector is particularly insidious as it leverages the content-type mail header field, which is commonly used by email clients to determine how to display different parts of an email message. The demonstration of this vulnerability using read_body.php highlights how the flaw manifests when the application attempts to render email content without proper security controls.
The technical implementation of this vulnerability involves the application's failure to properly escape or filter user-supplied data from email headers before rendering it in the web interface. When SquirrelMail processes emails with specially crafted content-type headers, the mime.php script does not adequately sanitize the input, allowing malicious script code to be executed within the context of a victim's browser session. This occurs because the application assumes that email headers are benign and fails to implement proper HTML escaping or context-aware output encoding. The vulnerability is classified under CWE-79 as a failure to sanitize or incorrectly sanitizing user-controlled data, making it a direct implementation of the well-known cross-site scripting pattern. The flaw operates at the application layer and can be exploited through various email client configurations that do not properly validate header fields.
The operational impact of CVE-2004-0520 extends beyond simple script execution, as it enables attackers to perform session hijacking, credential theft, and data exfiltration from authenticated users. An attacker could craft malicious emails containing JavaScript payloads that would execute when a victim views the email in their SquirrelMail interface, potentially stealing cookies, session tokens, or redirecting users to malicious sites. This vulnerability particularly affects organizations relying on SquirrelMail for email services, as it can be exploited without requiring special privileges or direct access to the mail server. The attack can be carried out through simple email delivery, making it highly scalable and difficult to detect. According to ATT&CK framework, this vulnerability maps to T1566 (Phishing) and T1059 (Command and Scripting Interpreter) where attackers can leverage the XSS condition to execute malicious scripts and establish persistent access to user accounts. The vulnerability's exploitation does not require complex attack chains, making it a significant risk for any organization using vulnerable SquirrelMail versions.
Mitigation strategies for this vulnerability center on immediate application updates to version 1.4.3 or later, which contain the necessary patches to address the XSS flaw. Organizations should implement proper input validation and output encoding mechanisms throughout the email processing pipeline, ensuring that all user-supplied data from email headers is properly sanitized before rendering. The implementation of Content Security Policy headers can provide additional defense-in-depth measures to prevent script execution even if the primary vulnerability is not fully patched. Security configurations should include disabling the display of potentially dangerous content types or implementing strict sanitization rules for header fields. System administrators should also consider implementing email filtering rules that can detect and block suspicious content-type headers. Regular security audits of webmail applications and proactive monitoring for similar vulnerabilities in legacy systems are essential practices to prevent exploitation of such flaws. The vulnerability serves as a reminder of the critical importance of input validation and output encoding in web applications, particularly those handling user-generated content through email protocols.