CVE-2018-18840 in SEMCMS PHP
Summary
by MITRE
XSS was discovered in SEMCMS PHP V3.4 via the SEMCMS_SeoAndTag.php?Class=edit&CF=SeoAndTag tag_indexmetatit parameter.
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Analysis
by VulDB Data Team • 04/07/2020
The vulnerability identified as CVE-2018-18840 represents a cross-site scripting flaw within SEMCMS PHP version 3.4 that specifically affects the SEMCMS_SeoAndTag.php script. This issue manifests when the application processes user input through the tag_indexmetatit parameter within the edit context of the SeoAndTag class. The vulnerability stems from insufficient input validation and output encoding mechanisms that fail to properly sanitize user-supplied data before incorporating it into dynamic web page content. Attackers can exploit this weakness by injecting malicious script code into the parameter, which then executes in the context of other users' browsers who view the affected page. The flaw falls under the CWE-79 category of Cross-Site Scripting, specifically representing a stored XSS vulnerability since the malicious payload is persisted in the application's data storage and executed upon subsequent page requests.
The technical implementation of this vulnerability demonstrates a classic input sanitization failure where the application directly incorporates user-provided parameters into HTML output without proper context-aware encoding. When a malicious user submits crafted input containing script tags or JavaScript code through the tag_indexmetatit parameter, the application fails to escape special characters or validate the input against a whitelist of acceptable values. This allows attackers to inject malicious payloads that can perform various harmful actions including session hijacking, credential theft, or redirection to malicious websites. The vulnerability is particularly concerning because it occurs within a content management system's administrative interface, potentially enabling attackers to escalate privileges or compromise the entire CMS installation. The ATT&CK framework categorizes this as a technique under T1059.007 for Command and Scripting Interpreter: JavaScript, and T1531 for Account Access Removal, as successful exploitation could lead to unauthorized access and privilege escalation within the system.
The operational impact of this vulnerability extends beyond simple data theft or defacement, as it creates a persistent threat vector that can be leveraged for advanced persistent threats. Once exploited, the malicious script can capture user sessions, redirect traffic to phishing sites, or even establish command and control channels for further attacks. The vulnerability affects the integrity and confidentiality of the CMS data, potentially compromising sensitive information stored within the system's database. Organizations running SEMCMS V3.4 are at risk of having their administrative interfaces compromised, which could lead to complete system takeover. The exploitation requires minimal technical skill and can be automated using existing attack frameworks, making it particularly dangerous in environments where multiple users interact with the CMS. Security professionals should note that this vulnerability aligns with the NIST Cybersecurity Framework's Protect function, specifically the PR.IP-1 and PR.IP-2 categories related to awareness and training, as well as the PR.DS-1 category concerning detection capabilities.
Mitigation strategies for CVE-2018-18840 should prioritize immediate patching of the SEMCMS application to the latest available version that addresses this specific vulnerability. Organizations should implement comprehensive input validation and output encoding measures, ensuring that all user-supplied data is properly sanitized before being rendered in web pages. The implementation of Content Security Policy headers can provide an additional layer of protection against XSS attacks by restricting script execution sources. Regular security audits and penetration testing should be conducted to identify similar vulnerabilities within the application's codebase. Additionally, organizations should establish proper web application firewall rules to detect and block suspicious requests containing common XSS payload patterns. The principle of least privilege should be enforced by limiting administrative access to only necessary personnel and implementing multi-factor authentication. Regular security updates and vulnerability assessments should be part of the organization's ongoing security posture management, as this vulnerability demonstrates the importance of keeping CMS platforms current with security patches. The remediation process should also include monitoring for any signs of exploitation attempts and implementing proper logging mechanisms to track access to the affected script and parameters.