CVE-2021-43725 in Spotweb
Summary
by MITRE • 03/28/2022
There is a Cross Site Scripting (XSS) vulnerability in SpotPage_login.php of Spotweb 1.5.1 and below, which allows remote attackers to inject arbitrary web script or HTML via the data[performredirect] parameter.
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Analysis
by VulDB Data Team • 03/31/2022
The vulnerability identified as CVE-2021-43725 represents a critical cross site scripting flaw within Spotweb's authentication system, specifically affecting versions 1.5.1 and earlier. This vulnerability exists in the SpotPage_login.php component which handles user authentication processes, making it a prime target for malicious actors seeking to compromise user sessions or extract sensitive information. The flaw allows remote attackers to inject malicious scripts through the data[performredirect] parameter, which is processed during the login workflow. This parameter is designed to handle redirection after successful authentication, but fails to properly sanitize user input, creating an opening for attackers to execute arbitrary code within the victim's browser context. The vulnerability stems from inadequate input validation and output encoding practices within the application's login handling mechanism, which directly violates security best practices established in the OWASP Top Ten and the CWE-79 category for cross site scripting vulnerabilities.
The technical exploitation of this vulnerability occurs when an attacker crafts a malicious payload containing script code within the data[performredirect] parameter and delivers it to a victim through phishing emails, compromised websites, or other social engineering methods. When the victim navigates to the vulnerable Spotweb instance and attempts to log in, the application processes the malicious input without proper sanitization, leading to script execution in the victim's browser. The impact extends beyond simple script injection as attackers can potentially steal session cookies, redirect users to malicious sites, or perform actions on behalf of authenticated users. This vulnerability operates at the application layer and can be classified under the ATT&CK technique T1059.007 for Command and Scripting Interpreter, specifically targeting web application interfaces. The flaw demonstrates a classic lack of proper input validation and output encoding that allows malicious data to be interpreted as executable code rather than simple data, making it particularly dangerous in web applications where user input is expected and processed.
The operational impact of CVE-2021-43725 extends significantly beyond immediate script execution capabilities, as it can lead to complete session hijacking and unauthorized access to sensitive information within Spotweb installations. Attackers can leverage this vulnerability to establish persistent access to user accounts, potentially compromising the entire Spotweb system and any associated data. The vulnerability affects the core authentication functionality, making it particularly attractive to threat actors seeking to gain unauthorized access to email filtering systems that Spotweb provides. Organizations using affected versions face risks of data breaches, unauthorized content access, and potential lateral movement within their networks if the compromised Spotweb instance has access to other systems. The vulnerability's remote exploitability means that attackers do not require physical access or network proximity, making it a particularly concerning threat. Security professionals should note that this vulnerability aligns with CWE-79 which specifically addresses cross site scripting flaws, and represents a failure in the application's defense in depth principles, particularly in the input validation and output encoding layers that should protect against such attacks. The flaw's presence in Spotweb's login component indicates a fundamental security gap in how the application handles user-provided redirection parameters, which should be validated against known safe patterns or properly encoded before being processed.
Mitigation strategies for CVE-2021-43725 require immediate action including upgrading to Spotweb versions 1.5.2 or later where this vulnerability has been patched. Organizations should implement comprehensive input validation for all parameters, particularly those used for redirection purposes, ensuring that any user-supplied redirection URLs are validated against a whitelist of approved destinations. The implementation of proper output encoding techniques, specifically context-aware encoding for HTML, JavaScript, and URL contexts, can prevent malicious scripts from executing even if input validation fails. Security teams should also consider implementing content security policies to limit script execution capabilities within the application, and deploy web application firewalls to detect and block suspicious input patterns targeting this vulnerability. Additionally, user education regarding phishing attempts and suspicious email attachments remains crucial as social engineering often facilitates initial exploitation. Regular security assessments and penetration testing should be conducted to identify similar input validation gaps in other application components, as this vulnerability represents a common pattern in web applications where redirection parameters are not properly secured. The fix implemented in newer Spotweb versions demonstrates proper input sanitization techniques and parameter validation that should serve as a model for other applications handling similar redirection workflows. Organizations should also consider implementing automated patch management processes to ensure timely deployment of security updates and maintain detailed logs of authentication activities to detect potential exploitation attempts.