CVE-2018-19206 in RoundCube
Summary
by MITRE
steps/mail/func.inc in Roundcube before 1.3.8 has XSS via crafted use of <svg><style>, as demonstrated by an onload attribute in a BODY element, within an HTML attachment.
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Analysis
by VulDB Data Team • 06/05/2023
The vulnerability identified as CVE-2018-19206 represents a cross-site scripting flaw discovered in Roundcube webmail software versions prior to 1.3.8. This vulnerability specifically affects the steps/mail/func.inc component and exploits a weakness in how the application processes HTML attachments. The flaw manifests when maliciously crafted HTML content containing svg and style elements is processed, particularly when these elements include onload attributes within BODY elements. This type of vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is classified as a critical security weakness in web applications where user-controllable data is not properly sanitized before being rendered in the browser.
The technical implementation of this vulnerability exploits the trust placed by the Roundcube application in HTML content contained within email attachments. When a user opens an email with a maliciously crafted HTML attachment, the application processes the content without adequate sanitization of potentially dangerous elements. The specific attack vector involves embedding SVG elements with embedded style definitions that can contain JavaScript execution hooks, particularly leveraging the onload attribute that executes code when the HTML element loads. This vector allows attackers to bypass standard input validation mechanisms that might otherwise filter out obvious script tags, as the malicious code is embedded within less obvious HTML structures that are still valid and rendered by modern browsers.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to perform a range of malicious activities including session hijacking, data exfiltration, and redirection to malicious sites. When a user accesses an infected email attachment, the malicious code executes in the context of the user's session, potentially allowing unauthorized access to sensitive email content, personal information, and communication data. This vulnerability particularly affects enterprise environments where email is a primary communication channel and users may inadvertently open malicious attachments from phishing campaigns or compromised sources. The attack requires minimal user interaction beyond opening the infected email, making it particularly dangerous in social engineering contexts where users may trust the source of the email.
Mitigation strategies for CVE-2018-19206 should prioritize immediate patching of Roundcube installations to version 1.3.8 or later, which includes proper sanitization of HTML content in email attachments. Organizations should implement comprehensive email filtering solutions that scan attachments for malicious HTML content and employ content security policies to prevent script execution. Network administrators should consider implementing web application firewalls that can detect and block attempts to exploit XSS vulnerabilities. The vulnerability demonstrates the importance of proper input validation and output encoding in web applications, aligning with ATT&CK technique T1203 for Exploitation for Credential Access and T1566 for Phishing. Security teams should also consider implementing user education programs to reduce the risk of successful social engineering attacks that leverage such vulnerabilities, as the attack chain typically involves user interaction with malicious email content.