CVE-2021-27310 in Clansphere
Summary
by MITRE • 03/24/2021
Clansphere CMS 2011.4 allows unauthenticated reflected XSS via "language" parameter.
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Analysis
by VulDB Data Team • 04/04/2021
The vulnerability identified as CVE-2021-27310 affects Clansphere CMS version 2011.4 and represents a critical security flaw that enables unauthenticated reflected cross-site scripting attacks. This vulnerability specifically targets the "language" parameter within the application's input handling mechanisms, creating a pathway for malicious actors to inject and execute arbitrary JavaScript code in the context of victim browsers. The flaw exists due to insufficient validation and sanitization of user-supplied input parameters, allowing attackers to craft malicious URLs that when visited by unsuspecting users, trigger the execution of malicious scripts within the victim's browser environment.
The technical implementation of this vulnerability stems from the CMS's failure to properly escape or filter special characters in the language parameter before incorporating it into web responses. When a user visits a URL containing malicious script within the language parameter, the application reflects this script back to the user's browser without adequate sanitization measures. This reflected nature means that the malicious payload is not stored on the server but rather injected through the request itself, making it particularly dangerous as it can be delivered via email links, chat messages, or any other means that directs users to the vulnerable endpoint. The vulnerability falls under CWE-79 which specifically addresses Cross-Site Scripting flaws, and aligns with ATT&CK technique T1566.001 for initial access through spearphishing attachments or links, making it a significant vector for social engineering campaigns.
The operational impact of this vulnerability extends beyond simple script execution as it can enable attackers to perform a wide range of malicious activities including session hijacking, credential theft, data exfiltration, and redirection to malicious sites. An attacker could craft payloads that steal session cookies, redirect users to phishing pages, or inject malware delivery mechanisms directly into the victim's browser. The unauthenticated nature of this vulnerability means that no prior access or credentials are required to exploit it, making it particularly dangerous for public-facing applications. Given that Clansphere CMS is a content management system often used for community websites, forums, and collaborative platforms, the potential for widespread impact increases significantly as these systems frequently contain sensitive user information and may be accessed by numerous users.
Mitigation strategies for this vulnerability should focus on implementing robust input validation and output encoding mechanisms throughout the application. The primary fix involves sanitizing all user-supplied input parameters, particularly the language parameter, by implementing proper HTML entity encoding before any output is rendered to the browser. Additionally, organizations should implement Content Security Policy headers to limit the sources from which scripts can be loaded and executed. Regular security audits and input validation testing should be conducted to identify similar vulnerabilities in other parameters or components. The vulnerability also highlights the importance of keeping CMS platforms updated, as this specific version of Clansphere CMS appears to be outdated and may contain other unpatched security issues. Implementing web application firewalls and security monitoring systems can help detect and block malicious requests attempting to exploit this vulnerability, while user education about avoiding suspicious links remains a crucial defensive measure in preventing successful exploitation attempts.