CVE-2017-6820 in RoundCube
Summary
by MITRE
rcube_utils.php in Roundcube before 1.1.8 and 1.2.x before 1.2.4 is susceptible to a cross-site scripting vulnerability via a crafted Cascading Style Sheets (CSS) token sequence within an SVG element.
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Analysis
by VulDB Data Team • 08/25/2024
The vulnerability identified as CVE-2017-6820 represents a cross-site scripting flaw in Roundcube webmail software that affects versions prior to 1.1.8 and 1.2.4. This security weakness resides within the rcube_utils.php file and specifically targets the handling of Cascading Style Sheets CSS token sequences within SVG elements. The vulnerability allows attackers to inject malicious code through carefully crafted SVG content that contains CSS directives, potentially enabling unauthorized access to user sessions and data exposure. Such vulnerabilities are particularly dangerous in webmail applications where users frequently interact with potentially untrusted content from external sources.
The technical implementation of this vulnerability stems from inadequate input validation and sanitization of SVG content within the Roundcube application's utility functions. When the application processes SVG elements containing CSS tokens, it fails to properly escape or filter these sequences, allowing malicious CSS code to persist in the rendered output. This flaw operates under the CWE-79 category of Cross-Site Scripting, specifically manifesting as a stored XSS vulnerability where malicious payloads can be embedded within SVG files and executed when users view them. The attack vector leverages the browser's interpretation of SVG elements and their associated CSS properties, which can contain executable JavaScript code when improperly sanitized.
The operational impact of this vulnerability extends beyond simple script execution, as it can lead to complete session hijacking, data theft, and unauthorized access to sensitive email communications. An attacker could craft malicious SVG attachments or embedded content that, when viewed by a victim, would execute malicious JavaScript code within the context of the victim's authenticated session. This could result in the compromise of email accounts, access to confidential communications, and potential lateral movement within organizational networks where Roundcube is deployed. The vulnerability is particularly concerning because email systems are often considered trusted by users, making social engineering attacks more effective when combined with such technical exploits.
Organizations using Roundcube versions affected by CVE-2017-6820 should immediately implement the available patches and updates to remediate this vulnerability. The recommended mitigation includes upgrading to Roundcube version 1.1.8 or 1.2.4, which contain proper input sanitization and CSS token filtering mechanisms. Additionally, administrators should implement content security policies that restrict the execution of inline scripts and embedded SVG content where possible. Network-level protections such as web application firewalls can provide additional defense-in-depth measures, while user education about suspicious email attachments and embedded content remains crucial. The ATT&CK framework categorizes this vulnerability under T1059.007 for Scripting and T1566 for Phishing, highlighting the multi-faceted nature of the threat landscape that this vulnerability enables. Organizations should also consider implementing automated scanning tools to identify and remediate similar vulnerabilities in other web applications within their environment.