Vulnerability DatabaseCVE-2023-5631

CVE-2023-5631:
Linux Debian vulnerability analysis and mitigation

Overview

CVE-2023-5631 is a cross-site scripting (XSS) vulnerability affecting Roundcube webmail versions before 1.4.15, 1.5.x before 1.5.5, and 1.6.x before 1.6.4. The vulnerability exists in the handling of SVG documents within HTML email messages, specifically in the program/lib/Roundcube/rcube_washtml.php component. The vulnerability was discovered and reported separately by Matthieu Faou (ESET) and Denys Klymenko in October 2023 (Roundcube News, NVD).

Technical details

The vulnerability allows stored XSS via an HTML email message containing a crafted SVG document. The issue stems from improper sanitization of HTML messages in the rcube_washtml.php component. When a malicious email is viewed in a web browser, it can trigger the execution of arbitrary JavaScript code in the context of the user's browser session without requiring any additional user interaction (ESET Report, Debian Advisory). The vulnerability has been assigned a CVSS v3.1 base score of 6.1 (Medium) by ESET and 5.4 (Medium) by NVD (NVD).

Impact

The vulnerability allows remote attackers to execute arbitrary JavaScript code in the context of the user's browser session. This could potentially lead to the theft of email data, user credentials, and authentication tokens. The vulnerability is particularly concerning as it requires no user interaction beyond viewing the malicious email message (ESET Report).

Mitigation and workarounds

The vulnerability has been fixed in Roundcube versions 1.4.15, 1.5.5, and 1.6.4. System administrators are strongly recommended to upgrade to these or newer versions immediately. The fix involves improved sanitization of SVG content in HTML messages (Roundcube News). Various Linux distributions have also released security updates, including Debian (versions 1.4.15+dfsg.1-1~deb11u1 for bullseye and 1.6.4+dfsg-1~deb12u1 for bookworm) and Fedora (Debian Advisory, Fedora Update).

Community reactions

The vulnerability has received significant attention due to its active exploitation by the Winter Vivern APT group. Security researchers have noted that this represents an escalation in the group's capabilities, as they previously relied on known vulnerabilities rather than zero-days. The vulnerability has been added to CISA's Known Exploited Vulnerabilities Catalog, requiring federal agencies to apply fixes (NVD).