CVE-2006-5652 in iPlanet Messaging Server Messenger Express
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Sun iPlanet Messaging Server Messenger Express allows remote attackers to inject arbitrary web script via the expression Cascading Style Sheets (CSS) function, as demonstrated by setting the width style for an IMG element. NOTE: this issue might be related to CVE-2006-5486, however due to the vagueness of the initial advisory and different researchers, it has been assigned a new CVE.
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Analysis
by VulDB Data Team • 04/26/2026
The CVE-2006-5652 vulnerability represents a critical cross-site scripting flaw discovered in Sun iPlanet Messaging Server Messenger Express, a web-based email client application that was widely deployed in enterprise environments during the mid-2000s. This vulnerability specifically targets the application's handling of Cascading Style Sheets functionality, particularly when processing the width style attribute for image elements. The flaw demonstrates how seemingly benign CSS processing can become a vector for malicious code execution, highlighting the complex security implications that arise when web applications process user-supplied content through styling mechanisms. The vulnerability's classification as a persistent XSS issue means that malicious scripts could be stored and executed against unsuspecting users who viewed affected content, potentially leading to session hijacking, credential theft, or other malicious activities.
The technical exploitation of this vulnerability occurs through the CSS width style attribute manipulation within image elements, where an attacker can inject malicious JavaScript code that gets executed when the affected web application renders the styled content. This particular attack vector operates by leveraging the application's insufficient input validation and output encoding mechanisms when processing CSS properties. The vulnerability stems from the application's failure to properly sanitize user-supplied CSS content, particularly when it processes the width attribute of img tags. This flaw aligns with CWE-79, which specifically addresses Cross-Site Scripting vulnerabilities, and demonstrates how CSS-based injection techniques can bypass traditional input validation measures. The vulnerability's exploitation requires minimal user interaction beyond viewing the maliciously crafted email content, making it particularly dangerous in mass email scenarios where users might inadvertently trigger the malicious code execution.
The operational impact of CVE-2006-5652 extends beyond simple script injection, as it represents a significant threat to enterprise email security infrastructure and user privacy. Organizations utilizing Sun iPlanet Messaging Server Messenger Express were potentially exposed to persistent security breaches where attackers could establish backdoors, steal user credentials, or redirect users to malicious websites. The vulnerability's potential for mass impact increases when considering that email systems often serve as primary communication channels for organizations, making them attractive targets for social engineering campaigns. Security researchers have noted that this vulnerability could be exploited in conjunction with other attack vectors, potentially leading to privilege escalation or lateral movement within network environments. The issue's relationship to CVE-2006-5486 demonstrates how similar vulnerabilities in the same product family can compound security risks, creating cascading effects that extend beyond individual applications.
Mitigation strategies for CVE-2006-5652 require comprehensive security measures including immediate application patching, input validation enhancements, and output encoding improvements. Organizations should implement strict CSS content filtering mechanisms that sanitize all user-supplied styling information, particularly focusing on attributes that can execute scripts or redirect content. The remediation approach should align with ATT&CK technique T1059.007, which addresses script execution through web applications, by implementing proper input sanitization and validation controls. Security teams must also consider deploying web application firewalls and implementing Content Security Policy headers to prevent unauthorized script execution. Regular security assessments and penetration testing should be conducted to identify similar vulnerabilities in legacy applications, as this vulnerability demonstrates how older web technologies can contain dangerous security flaws. The incident underscores the importance of maintaining up-to-date security patches and implementing robust security controls even for legacy systems that may no longer receive official support.