CVE-2026-2971 is a cross-site scripting vulnerability identified in the Smart-SSO product by a466350665, specifically affecting versions 2.1.0 and 2.1.1. The vulnerability resides in the login.html template file within the smart-sso-server component, where the redirectUri parameter is improperly sanitized. An attacker can craft a malicious URL containing a manipulated redirectUri argument that, when visited by a user, executes arbitrary JavaScript in the victim's browser context. This type of reflected XSS attack can be performed remotely without requiring authentication, but it does require user interaction, such as clicking a malicious link. The vulnerability impacts the confidentiality and integrity of user sessions by enabling potential session hijacking, credential theft, or phishing attacks. The vendor was contacted early but did not respond or provide a patch, leaving the vulnerability unmitigated. The CVSS 4.0 vector indicates low attack complexity and no privileges or user interaction required for the attacker, except that the victim must interact with the malicious link. No known exploits have been observed in the wild, but proof-of-concept exploits have been publicly disclosed. The lack of vendor response increases the urgency for organizations to implement their own mitigations. This vulnerability highlights the importance of proper input validation and output encoding in web applications, especially in authentication-related components like single sign-on systems.

The primary impact of CVE-2026-2971 is the potential compromise of user sessions and credentials through cross-site scripting attacks. Successful exploitation can lead to session hijacking, allowing attackers to impersonate legitimate users and access sensitive resources. It can also facilitate phishing attacks by injecting malicious scripts that alter the login page or redirect users to fraudulent sites. For organizations relying on Smart-SSO for centralized authentication, this vulnerability undermines trust in their identity management infrastructure and could lead to unauthorized access to multiple connected systems. The medium CVSS score reflects moderate risk, but the real-world impact depends on the deployment scale of Smart-SSO and the sensitivity of protected resources. Since the vulnerability requires user interaction, social engineering is a likely attack vector. The absence of vendor patches increases exposure time, potentially inviting targeted attacks against organizations using affected versions. Overall, the vulnerability poses a significant risk to confidentiality and integrity of authentication processes and user data.

To mitigate CVE-2026-2971, organizations should implement strict input validation and output encoding on the redirectUri parameter to prevent injection of malicious scripts. Employing Content Security Policy (CSP) headers can reduce the impact of XSS by restricting the execution of unauthorized scripts. Web Application Firewalls (WAFs) should be configured to detect and block suspicious payloads targeting the redirectUri parameter. Since no official patch is available, consider temporarily disabling or restricting the use of the redirectUri parameter if feasible. Educate users to be cautious about clicking unsolicited links, especially those related to login pages. Conduct thorough security testing of the Smart-SSO deployment to identify any other potential injection points. Monitor logs for unusual access patterns or attempts to exploit this vulnerability. Finally, maintain communication with the vendor for any future updates or patches and plan for an upgrade once a fix is released.