CVE-2017-9305 in Wiki CMS Groupware
Summary
by MITRE
lib/core/TikiFilter/PreventXss.php in Tiki Wiki CMS Groupware 16.2 allows remote attackers to bypass the XSS filter via padded zero characters, as demonstrated by an attack on tiki-batch_send_newsletter.php.
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Analysis
by VulDB Data Team • 12/07/2022
The vulnerability identified as CVE-2017-9305 resides within the Tiki Wiki CMS Groupware version 16.2, specifically in the file lib/core/TikiFilter/PreventXss.php which is responsible for implementing cross-site scripting protection mechanisms. This flaw represents a critical security weakness that undermines the application's ability to properly sanitize user input and prevent malicious script execution in web browsers. The vulnerability exploits a fundamental weakness in the input validation logic that fails to adequately handle specially crafted input containing padded zero characters.
The technical implementation of this vulnerability stems from insufficient input sanitization within the XSS prevention system. When user-supplied data is processed through the TikiFilter component, the presence of padded zero characters allows attackers to bypass the intended filtering mechanisms. These null padding characters are not properly stripped or recognized by the validation logic, enabling malicious payloads to slip through the security checks that should prevent cross-site scripting attacks. The vulnerability specifically manifests in the tiki-batch_send_newsletter.php endpoint, which accepts user input for newsletter distribution and processes it through the vulnerable filtering system.
The operational impact of this vulnerability is significant as it allows remote attackers to execute arbitrary JavaScript code within the context of other users' browsers. This bypass enables attackers to perform actions such as stealing session cookies, redirecting users to malicious websites, defacing content management interfaces, or conducting more sophisticated attacks like credential harvesting. The attack vector is particularly concerning because it can be executed remotely without requiring authentication, making it accessible to anyone who can interact with the vulnerable Tiki Wiki CMS instance. This weakness directly violates the principle of least privilege and undermines the web application's security posture.
The vulnerability maps to CWE-79 which specifically addresses Cross-site Scripting flaws in web applications, and aligns with ATT&CK technique T1213 which covers data from information repositories. Organizations running Tiki Wiki CMS Groupware 16.2 should immediately implement mitigations including updating to patched versions, implementing additional input validation layers, and deploying web application firewalls to monitor for suspicious input patterns. The recommended remediation strategy involves strengthening the input sanitization logic to properly handle null characters and other special padding sequences while maintaining the application's core functionality. Security teams should also conduct comprehensive testing to ensure that similar padding vulnerabilities do not exist in other input validation components throughout the application.