CVE-2017-8384 in Craft
Summary
by MITRE
Craft CMS before 2.6.2976 allows XSS attacks because an array returned by HttpRequestService::getSegments() and getActionSegments() need not be zero-based. NOTE: this vulnerability exists because of an incomplete fix for CVE-2017-8052.
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Analysis
by VulDB Data Team • 09/22/2020
The vulnerability identified as CVE-2017-8384 affects Craft CMS versions prior to 2.6.2976 and represents a cross-site scripting vulnerability that stems from improper handling of array indexing within the HttpRequestService class. This issue specifically involves the getSegments() and getActionSegments() methods which return arrays that are not guaranteed to be zero-based, creating a potential vector for malicious input manipulation. The vulnerability serves as an incomplete remediation of CVE-2017-8052, indicating that the initial fix was insufficient in addressing all possible attack vectors within the application's request handling mechanisms. This oversight creates a persistent security weakness that attackers can exploit to execute malicious scripts within the context of a victim's browser session.
The technical flaw manifests when the application processes URL segments and action segments from HTTP requests without ensuring proper array indexing alignment. When HttpRequestService::getSegments() or getActionSegments() return arrays that do not start with a zero index, the application's subsequent processing logic fails to properly validate or sanitize these array elements before incorporating them into dynamic content generation. This improper array handling creates a condition where attacker-controlled input can bypass intended security controls and be rendered as executable JavaScript within the user's browser. The vulnerability operates at the application layer where HTTP request parameters are parsed and processed, making it particularly dangerous as it can be triggered through standard web browsing activities without requiring specialized tools or techniques.
The operational impact of this vulnerability extends beyond simple XSS execution to potentially enable more sophisticated attack vectors including session hijacking, credential theft, and privilege escalation within the Craft CMS environment. An attacker can craft malicious URLs that exploit the zero-based array indexing flaw to inject malicious scripts that execute in the context of authenticated users, potentially leading to complete compromise of the affected CMS instances. The vulnerability is particularly concerning because it affects core request handling functionality that is fundamental to how the CMS processes user input, meaning that any page or feature that relies on URL segment parsing could serve as an attack surface. The incomplete nature of the previous fix for CVE-2017-8052 suggests that security teams may have prematurely assumed the issue was resolved, leading to a false sense of security that could result in prolonged exposure.
Organizations should immediately upgrade to Craft CMS version 2.6.2976 or later to address this vulnerability, as the patch includes proper array indexing validation and sanitization mechanisms. Security measures should include implementing proper input validation at all entry points where user-supplied data is processed, particularly focusing on URL segment handling and HTTP request parameter parsing. The vulnerability aligns with CWE-79 which describes cross-site scripting flaws, and can be mapped to ATT&CK technique T1203 which involves exploiting web application vulnerabilities to execute malicious code. Additional mitigations include deploying web application firewalls to monitor for suspicious URL patterns, implementing content security policies to restrict script execution, and conducting regular security assessments of application code to identify similar array indexing issues. The remediation process should also involve reviewing all custom modules and plugins that may interact with the HttpRequestService to ensure they do not introduce similar vulnerabilities through improper array handling practices.