CVE-2006-5653 in Java System Messenger Express
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the errorHTML function in the index script in Sun Java System Messenger Express 6 allows remote attackers to inject arbitrary web script or HTML via the error parameter. NOTE: this issue might be related to CVE-2006-5486, however due to the vagueness of the initial advisory and different researchers a new CVE was assigned.
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Analysis
by VulDB Data Team • 04/26/2026
The vulnerability described in CVE-2006-5653 represents a critical cross-site scripting flaw within Sun Java System Messenger Express 6, specifically within the errorHTML function of the index script. This vulnerability arises from insufficient input validation and sanitization of the error parameter, creating an exploitable condition that allows remote attackers to inject malicious web scripts or HTML content directly into the application's error handling mechanism. The flaw exists at the application layer where user-supplied input is not properly escaped or filtered before being rendered in the web response, making it susceptible to client-side code injection attacks.
The technical implementation of this vulnerability stems from the improper handling of error messages within the Messenger Express application's index script. When the application encounters an error condition, it processes the error parameter through the errorHTML function without adequate sanitization of user-provided input. This creates a direct path for malicious actors to inject JavaScript code or HTML elements that will execute in the context of other users' browsers who encounter the error page. The vulnerability is classified as a classic reflected XSS attack where the malicious payload is embedded in the error parameter and executed when the vulnerable application generates an error response. This issue maps directly to CWE-79, which specifically addresses Cross-Site Scripting vulnerabilities, and demonstrates the fundamental weakness in input validation and output encoding practices.
The operational impact of this vulnerability extends beyond simple data theft or defacement, as it can enable sophisticated attack chains that compromise user sessions and facilitate further exploitation. Attackers can craft malicious error parameters that, when processed by the vulnerable application, execute scripts in the victim's browser context. This capability allows for session hijacking, credential theft, and the potential installation of backdoors or malware. The vulnerability affects all users of the Messenger Express 6 application who may encounter error conditions, making it particularly dangerous in environments where the application serves a large user base. The attack vector is straightforward and requires minimal technical expertise, as the vulnerability can be exploited through simple parameter manipulation without authentication requirements. This aligns with ATT&CK technique T1566.001, which describes the use of malicious content to gain initial access through web-based attacks.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term architectural improvements to prevent similar issues. The primary fix involves implementing proper input sanitization and output encoding within the errorHTML function, ensuring that all user-supplied parameters are properly escaped before being incorporated into error messages. Organizations should implement strict parameter validation that rejects or sanitizes potentially malicious input patterns, particularly those containing script tags or other HTML/JavaScript elements. Additionally, the application should employ Content Security Policy headers to prevent unauthorized script execution, and regular security testing should be conducted to identify similar vulnerabilities in other application components. The vulnerability also highlights the importance of secure coding practices and input validation at all levels of application development, particularly in error handling routines where user input is processed without proper sanitization.