CVE-2011-2023 in SquirrelMail
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in functions/mime.php in SquirrelMail before 1.4.22 allows remote attackers to inject arbitrary web script or HTML via a crafted STYLE element in an e-mail message.
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Analysis
by VulDB Data Team • 11/14/2021
The vulnerability identified as CVE-2011-2023 represents a critical cross-site scripting flaw in the SquirrelMail webmail application that affected versions prior to 1.4.22. This vulnerability resides within the functions/mime.php file, which processes email content and handles various MIME types during message rendering. The flaw specifically targets how the application processes STYLE elements within email messages, creating an avenue for malicious actors to execute arbitrary web scripts or HTML code in the context of authenticated users' browsers. The vulnerability is particularly concerning because it operates at the email message parsing level, where user input is processed without adequate sanitization, allowing attackers to craft malicious emails that can compromise user sessions and data confidentiality.
The technical exploitation of this vulnerability follows a classic XSS attack pattern where the attacker crafts an email message containing a malicious STYLE element designed to bypass the application's input validation mechanisms. When a victim accesses this specially crafted email through the vulnerable SquirrelMail interface, the browser renders the malicious content within the email display area, executing the injected script in the context of the victim's session. This allows attackers to perform actions such as stealing session cookies, redirecting users to malicious websites, or modifying the email interface to capture user credentials. The vulnerability is categorized under CWE-79 as a failure to sanitize user input, specifically in the context of web application security where dynamic content is rendered without proper filtering of potentially malicious elements.
The operational impact of CVE-2011-2023 extends beyond simple script execution, as it provides attackers with a persistent vector for more sophisticated attacks within the email environment. Since SquirrelMail is widely used in enterprise and organizational settings, this vulnerability could enable attackers to compromise user accounts, access sensitive email communications, and potentially escalate privileges within the email infrastructure. The attack surface is particularly broad given that email is a fundamental communication tool, making successful exploitation likely to affect numerous users and organizations. The vulnerability also aligns with ATT&CK technique T1566, which describes the use of spearphishing with malicious attachments or links, where the malicious content is embedded within the email message itself rather than requiring external delivery mechanisms.
Organizations utilizing vulnerable versions of SquirrelMail should immediately implement the patch released with version 1.4.22, which addresses the input sanitization issue by properly filtering and escaping STYLE elements within email content. Additional mitigations include implementing strict email content filtering policies, enabling security headers such as Content Security Policy to limit script execution, and conducting regular security assessments of webmail applications. Network-level protections such as email gateway filtering and web application firewalls can provide additional defense-in-depth measures. The vulnerability also underscores the importance of maintaining up-to-date web applications and implementing comprehensive input validation across all user-facing interfaces, as the flaw demonstrates how insufficient sanitization in one component can create widespread security implications throughout the application stack.