CVE-2026-2971: A466350665 Smart-sso XSS Vulnerability

CVE-2026-2971 Overview

A reflected Cross-Site Scripting (XSS) vulnerability has been identified in a466350665 Smart-SSO, an open-source Single Sign-On solution. The vulnerability exists in the login functionality where the redirectUri parameter is not properly sanitized, allowing attackers to inject malicious scripts that execute in the context of a victim's browser session. This flaw affects the login template file at smart-sso-server/src/main/resources/templates/login.html and can be exploited remotely without authentication.

Critical Impact

Attackers can leverage this XSS vulnerability to steal session tokens, hijack user accounts, perform phishing attacks, or execute arbitrary actions on behalf of authenticated users within the SSO environment.

Affected Products

• a466350665 Smart-SSO versions up to and including 2.1.1
• Smart-SSO Server login component (login.html template)
• Applications relying on Smart-SSO for authentication services

Discovery Timeline

• 2026-02-23 - CVE-2026-2971 published to NVD
• 2026-02-25 - Last updated in NVD database

Technical Details for CVE-2026-2971

Vulnerability Analysis

This vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation), commonly known as Cross-Site Scripting. The affected component fails to properly sanitize user-controlled input in the redirectUri parameter before rendering it in the login page template. When a user accesses a crafted URL containing malicious JavaScript in the redirectUri parameter, the script executes within the user's browser context.

The vulnerability is particularly concerning in an SSO environment because successful exploitation could compromise not just the SSO server but potentially all connected applications that rely on Smart-SSO for authentication. The attack requires no privileges or authentication, only user interaction to click on a malicious link.

Root Cause

The root cause of this vulnerability is insufficient input validation and output encoding in the login.html template file located at smart-sso-server/src/main/resources/templates/login.html. The redirectUri parameter is directly reflected in the rendered HTML page without proper sanitization or encoding, allowing script injection. This represents a classic reflected XSS scenario where untrusted data is included in HTTP responses without appropriate escaping.

Attack Vector

The attack is network-based and requires user interaction. An attacker crafts a malicious URL containing JavaScript code within the redirectUri parameter and distributes it to potential victims through phishing emails, malicious websites, or social engineering tactics. When a victim clicks the link and the login page renders, the malicious script executes in their browser with access to cookies, session tokens, and DOM elements of the Smart-SSO application.

The vulnerability has been publicly documented with exploit details available, as indicated in the Notion Analysis on Smart SSO XSS.

Detection Methods for CVE-2026-2971

Indicators of Compromise

• Suspicious URL requests to Smart-SSO login endpoints containing encoded script tags or JavaScript event handlers in the redirectUri parameter
• Anomalous authentication patterns following user access to SSO login pages with unusual query strings
• Web application firewall (WAF) logs showing XSS payload patterns targeting the login endpoint
• Session token theft or unauthorized session creation following suspicious login page access

Detection Strategies

• Implement WAF rules to detect and block common XSS payloads in query parameters, particularly targeting redirectUri
• Deploy endpoint detection and response (EDR) solutions like SentinelOne to monitor for browser-based attacks and credential theft
• Review web server access logs for requests containing suspicious characters or encoded payloads in the redirectUri parameter
• Monitor authentication logs for anomalies such as session tokens being used from unexpected IP addresses or locations

Monitoring Recommendations

• Enable detailed logging for all Smart-SSO authentication endpoints and analyze patterns for potential exploitation attempts
• Configure Content Security Policy (CSP) headers and monitor for policy violations that may indicate script injection attempts
• Set up alerts for unusual patterns in redirectUri parameter values, such as those containing script tags, event handlers, or encoded characters
• Integrate SentinelOne Singularity XDR for comprehensive visibility into endpoint and network-level indicators of compromise

How to Mitigate CVE-2026-2971

Immediate Actions Required

• Implement strict input validation on the redirectUri parameter to allow only whitelisted redirect destinations
• Apply output encoding (HTML entity encoding) when rendering the redirectUri parameter in the login template
• Deploy a Web Application Firewall (WAF) with XSS detection rules as an interim protective measure
• Review and restrict the allowed redirect URLs to trusted domains only

Patch Information

As of the last update, the vendor (a466350665) was contacted about this disclosure but did not respond. No official patch is currently available. Organizations using Smart-SSO should implement the recommended workarounds below and monitor the VulDB entry for updates on vendor response or community patches.

Workarounds

• Implement server-side URL validation to ensure redirectUri only accepts URLs matching a predefined whitelist of trusted domains
• Apply proper output encoding using context-aware escaping in the Thymeleaf or template engine being used
• Deploy a reverse proxy or WAF with strict rules to filter and block malicious characters in query parameters
• Consider temporarily disabling the redirect functionality if it is not critical to operations until a proper fix is implemented

# Example Nginx WAF configuration to block common XSS patterns
location /login {
    if ($args ~* "(<script|javascript:|on\w+=)") {
        return 403;
    }
    
    # Restrict redirectUri to trusted domains
    if ($arg_redirectUri !~* "^https://(trusted-domain\.com|another-trusted\.com)") {
        return 400;
    }
    
    proxy_pass http://smart-sso-backend;
}