Impact Analysis

This vulnerability can allow an attacker to execute malicious JavaScript code in the context of the victim's webmail session if the victim previews a crafted HTML attachment. This can lead to unauthorized actions such as stealing session cookies, hijacking the user's session, or performing actions on behalf of the user.

Because the vulnerability requires user interaction (previewing the attachment), it is classified with user interaction required, but the impact includes potential compromise of confidentiality and integrity of the user's data within the webmail client.

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Executive Summary

This vulnerability is a cross-site scripting (XSS) issue in Roundcube Webmail versions before 1.5.14 and 1.6.14. It occurs because the software does not sufficiently sanitize HTML attachments when previewing them. Specifically, if a victim previews a text/html attachment, malicious scripts embedded in the attachment could execute.

The vulnerability was addressed by adding a strict Content Security Policy (CSP) header that prevents the execution of any JavaScript within the HTML attachment preview, effectively mitigating the XSS risk.

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Detection Guidance

This vulnerability involves cross-site scripting (XSS) in the preview of HTML attachments in Roundcube Webmail before versions 1.5.14 and 1.6.14. Detection typically involves verifying if the system is running a vulnerable version of Roundcube Webmail and testing if HTML attachments can execute scripts during preview.

You can check the installed Roundcube version with commands like:

• rpm -qa | grep roundcube
• dpkg -l | grep roundcube

To detect the vulnerability more actively, you could attempt to preview a crafted HTML attachment containing a benign script payload in a controlled environment and observe if the script executes.

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Mitigation Strategies

The vulnerability is mitigated by applying the security fix that adds a strict Content Security Policy (CSP) header to prevent execution of JavaScript in HTML attachment previews.

Immediate mitigation steps include:

• Upgrade Roundcube Webmail to version 1.5.14, 1.6.14, or later where the fix is included.
• Ensure the patch that adds the header `Content-Security-Policy: script-src 'none'` to the `display_uploaded_file` function in the relevant Roundcube files (`program/include/rcmail_action.php` or `program/lib/Roundcube/rcube_uploads.php`) is applied.
• If upgrading immediately is not possible, consider disabling HTML attachment preview functionality temporarily to prevent exploitation.

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Compliance Impact

The vulnerability is a cross-site scripting (XSS) issue in Roundcube Webmail related to insufficient sanitization of HTML attachments in preview mode. Such XSS vulnerabilities can potentially lead to unauthorized access to user data or session hijacking.

While the provided information does not explicitly mention compliance with standards like GDPR or HIPAA, XSS vulnerabilities generally pose risks to data confidentiality and integrity, which are critical aspects of these regulations.

Therefore, if exploited, this vulnerability could impact compliance by exposing personal or sensitive information through malicious script execution in the webmail client.

The fix involves adding a strict Content Security Policy (CSP) header to prevent script execution in HTML attachment previews, mitigating the risk and helping maintain compliance with security requirements.

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