CVE-2018-18841 in SEMCMS PHP
Summary
by MITRE
XSS was discovered in SEMCMS PHP V3.4 via the SEMCMS_SeoAndTag.php?Class=edit&CF=SeoAndTag tag_indexkey parameter.
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Analysis
by VulDB Data Team • 04/08/2020
The vulnerability identified as CVE-2018-18841 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 the tag_indexkey parameter through the Class=edit&CF=SeoAndTag URL structure, creating a dangerous condition where user-supplied input is not properly sanitized before being rendered back to the browser. The vulnerability falls under the category of reflected cross-site scripting as described in CWE-79, where malicious scripts are executed in the victim's browser through improperly validated input. The attack vector exploits the application's failure to implement proper output encoding or input validation mechanisms, allowing an attacker to inject malicious JavaScript code that persists in the application's administrative interface.
The technical implementation of this vulnerability stems from the application's insufficient sanitization of the tag_indexkey parameter, which is directly incorporated into the web page without appropriate HTML entity encoding or other protective measures. When an attacker crafts a malicious payload and submits it through this parameter, the application processes the input without validation, allowing the malicious code to be stored and subsequently executed whenever the affected page is accessed by an administrator or authenticated user. This creates a persistent threat where the injected script can perform actions such as stealing session cookies, redirecting users to malicious sites, or executing unauthorized administrative commands. The vulnerability demonstrates a classic weakness in web application security where input validation and output encoding are not consistently applied throughout the application's codebase, as outlined in the OWASP Top Ten 2017 category A03: Injection.
The operational impact of this vulnerability extends beyond simple script execution, as it provides attackers with a potential foothold for more sophisticated attacks within the application environment. An attacker who successfully exploits this vulnerability could gain access to administrative functions, modify content, or even escalate privileges within the SEMCMS system. The reflected nature of the vulnerability means that the attack requires user interaction, typically through phishing emails or social engineering tactics, where the victim must click on a malicious link containing the crafted payload. This makes the vulnerability particularly dangerous in environments where administrators frequently access potentially malicious links or where the application handles sensitive data. The vulnerability also aligns with ATT&CK technique T1566.001 for Phishing and T1059.007 for Command and Scripting Interpreter, as it enables both initial access through malicious payloads and execution of commands through the injected JavaScript.
Mitigation strategies for CVE-2018-18841 should focus on implementing comprehensive input validation and output encoding mechanisms throughout the SEMCMS application. The immediate fix involves sanitizing all user-supplied input through proper HTML entity encoding before rendering any content back to the browser, specifically targeting the tag_indexkey parameter in the SEMCMS_SeoAndTag.php script. Implementing Content Security Policy headers can provide additional defense-in-depth measures to prevent script execution, while regular security audits should be conducted to identify other potential input vectors that may suffer from similar vulnerabilities. Organizations should also ensure that all web applications undergo proper security testing including dynamic application security testing and manual code review to identify and remediate such injection flaws before they can be exploited. The vulnerability underscores the importance of following secure coding practices as recommended in the OWASP Secure Coding Practices and highlights the necessity of regular security updates and patch management to protect against known vulnerabilities in content management systems.