CVE-2005-4080 in IMP
Summary
by MITRE
Horde IMP 4.0.4 and earlier does not sanitize strings containing UTF16 null characters, which allows remote attackers to conduct cross-site scripting (XSS) attacks via UTF16 encoded attachments and strings that will be executed when viewed using Internet Explorer, which ignores the characters.
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Analysis
by VulDB Data Team • 01/04/2025
The vulnerability identified as CVE-2005-4080 affects Horde IMP version 4.0.4 and earlier, representing a critical cross-site scripting flaw that exploits improper input sanitization mechanisms. This vulnerability specifically targets the handling of UTF16 encoded strings within the email client's attachment processing functionality, creating a pathway for remote attackers to execute malicious scripts against unsuspecting users. The flaw leverages the unique behavior of Internet Explorer's rendering engine, which ignores UTF16 null characters during processing, allowing attackers to embed malicious code that remains undetected by standard sanitization routines.
The technical implementation of this vulnerability stems from the application's failure to properly sanitize user-supplied data containing UTF16 null characters during attachment processing. When a user views an email containing maliciously crafted UTF16 encoded content, the browser's handling of these null characters creates a vector for XSS exploitation. This occurs because the application's input validation routines do not account for the specific encoding behaviors of different browsers, particularly Internet Explorer's lenient parsing of UTF16 null bytes. The vulnerability falls under CWE-79 which categorizes improper neutralization of input during web output, specifically addressing cross-site scripting weaknesses in web applications.
The operational impact of this vulnerability extends beyond simple script execution, as it allows attackers to perform a range of malicious activities including session hijacking, credential theft, and redirection to malicious sites. Users who access compromised email attachments through Internet Explorer are particularly at risk since the browser's handling of UTF16 null characters creates a persistent execution environment for malicious payloads. The vulnerability demonstrates a fundamental flaw in the application's security model, where the assumption of uniform browser behavior leads to inadequate input validation and sanitization. Attackers can exploit this by crafting email attachments with UTF16 encoded strings that contain malicious JavaScript code, which executes when the attachment is viewed in the vulnerable browser environment.
Security professionals should implement multiple layers of defense to mitigate this vulnerability, beginning with immediate patching of affected Horde IMP versions to ensure proper UTF16 string sanitization. Organizations must also consider implementing content security policies that restrict script execution in email viewing environments, while network-level filtering can help identify and block malicious UTF16 encoded content. The ATT&CK framework categorizes this as a web application vulnerability exploitation technique, specifically under the T1211 category for exploitation for defense evasion. Additionally, regular security assessments should include testing for encoding-related vulnerabilities in web applications, as this flaw demonstrates the critical importance of considering browser-specific behaviors during security design phases. The vulnerability serves as a reminder that legacy applications often contain hidden security gaps that can be exploited through sophisticated encoding techniques, emphasizing the need for comprehensive security testing beyond standard input validation checks.