CVE-2025-63499: Alinto Sogo XSS Vulnerability

CVE-2025-63499 Overview

CVE-2025-63499 is a reflected Cross-Site Scripting (XSS) vulnerability affecting Alinto SOGo 5.12.3. The flaw resides in the handling of the theme parameter within the SOGo webmail interface, which fails to sanitize user-supplied input before rendering it in the response. An attacker can craft a malicious URL containing JavaScript payloads in the theme parameter and deliver it to an authenticated SOGo user. When the victim opens the link, arbitrary script executes in the context of the SOGo application, enabling session theft, credential harvesting, or unauthorized mailbox actions. The vulnerability is tracked under CWE-79: Improper Neutralization of Input During Web Page Generation.

Critical Impact
Successful exploitation allows attackers to execute arbitrary JavaScript in an authenticated SOGo user's browser session, potentially exposing mailbox contents and session credentials.

Affected Products

Alinto SOGo 5.12.3
SOGo groupware webmail interface
Deployments exposing the /SOGo/so/<user>/Mail/view endpoint

Discovery Timeline

2025-12-04 - CVE-2025-63499 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-63499

Vulnerability Analysis

SOGo is an open-source groupware server providing webmail, calendaring, and contact management. The theme query parameter controls the visual styling of the webmail view. In version 5.12.3, the application reflects the value of this parameter into the rendered HTML response without proper output encoding or input validation. This behavior enables reflected XSS attacks against authenticated users.

Because the vulnerability requires user interaction, attackers typically deliver the payload through phishing emails or malicious links. Once triggered, the injected script runs with the privileges of the target user's SOGo session. Attackers can exfiltrate session cookies, read mailbox contents, send messages on behalf of the victim, or pivot to further attacks against internal systems.

The EPSS score is 0.269% with a percentile of 18.606, indicating relatively low probability of active exploitation in the short term. No public exploitation in the wild has been confirmed.

Root Cause

The root cause is improper neutralization of user-controlled input in the theme parameter [CWE-79]. The SOGo view handler embeds the parameter value directly into the HTML output without HTML-entity encoding or context-aware escaping. As a result, JavaScript tags supplied by the attacker are parsed and executed by the victim's browser.

Attack Vector

Exploitation is network-based and requires user interaction. A representative attack URL takes the following form:

https://<sogo-host>/SOGo/so/<victim>/Mail/view?theme='<ScRiPt>alert(9998)</ScRiPt>

The attacker URL-encodes the payload and delivers it via email, chat, or a compromised web page. When the authenticated SOGo user clicks the link, the injected <script> element executes in the same origin as the SOGo application. See the public proof-of-concept repository for additional technical details.

Detection Methods for CVE-2025-63499

Indicators of Compromise

HTTP requests to /SOGo/so/*/Mail/view containing a theme parameter with HTML or script tags
URL-encoded payloads such as %3Cscript%3E, %3CScRiPt%3E, or %3Cimg%20onerror inside the theme parameter
Unexpected outbound requests from SOGo user sessions to attacker-controlled domains, indicating cookie exfiltration
Web server logs showing repeated crafted theme values from a single source IP

Detection Strategies

Deploy web application firewall (WAF) rules that inspect the theme query parameter for HTML tags and JavaScript event handlers
Enable server-side logging of all query parameters on the SOGo Mail/view endpoint and alert on non-alphanumeric values
Correlate authentication events with anomalous JavaScript-driven mailbox actions from the same session

Monitoring Recommendations

Monitor SOGo access logs for URL patterns matching XSS payload signatures
Track browser Content Security Policy (CSP) violation reports for the SOGo origin
Review email gateway logs for messages containing SOGo URLs with suspicious theme values

How to Mitigate CVE-2025-63499

Immediate Actions Required

Upgrade Alinto SOGo beyond version 5.12.3 once a patched release is available from the vendor
Restrict access to the SOGo webmail interface using VPN or IP allowlisting where feasible
Instruct users not to click SOGo links received from untrusted sources
Deploy a strict Content Security Policy on the SOGo origin to block inline script execution

Patch Information

No vendor advisory URL is listed in the NVD entry at publication time. Administrators should monitor the Alinto SOGo project and the SOGo source repository for security releases addressing the theme parameter handling in the Mail/view component.

Workarounds

Configure a reverse proxy (nginx, Apache, HAProxy) to filter or reject requests where the theme parameter contains characters outside [A-Za-z0-9_-]
Enforce a Content Security Policy header such as Content-Security-Policy: default-src 'self'; script-src 'self' on the SOGo origin
Enable HttpOnly and Secure flags on SOGo session cookies to limit cookie theft impact

bash

# Example nginx reverse proxy rule to block malicious theme values
location ~ ^/SOGo/so/.+/Mail/view {
    if ($arg_theme ~* "[<>\"'();]|script|onerror|onload") {
        return 400;
    }
    proxy_pass http://sogo_backend;
}