CVE-2015-6665 in Drupal
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in the Ajax handler in Drupal 7.x before 7.39 and the Ctools module 6.x-1.x before 6.x-1.14 for Drupal allows remote attackers to inject arbitrary web script or HTML via vectors involving a whitelisted HTML element, possibly related to the "a" tag.
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Analysis
by VulDB Data Team • 06/13/2022
The CVE-2015-6665 vulnerability represents a critical cross-site scripting flaw that affected Drupal 7.x versions prior to 7.39 and the Ctools module 6.x-1.x versions before 6.x-1.14. This vulnerability specifically targeted the Ajax handler component within these systems, creating a pathway for remote attackers to execute malicious scripts on affected websites. The flaw emerged from insufficient input validation and sanitization processes that were supposed to protect against malicious content injection, particularly when processing whitelisted HTML elements. The vulnerability's exploitation potential was significant as it allowed attackers to manipulate the content processing pipeline in ways that bypassed normal security controls.
The technical implementation of this vulnerability centered on the improper handling of HTML elements within the Ajax response processing mechanism. Attackers could craft malicious payloads that included whitelisted HTML tags such as the "a" tag, which are typically considered safe and allowed in content processing workflows. The vulnerability exploited the fact that while these elements were permitted in the system's whitelist, the sanitization process failed to properly validate the attributes and content associated with these elements. This created a scenario where malicious JavaScript code could be embedded within legitimate-looking HTML structures, particularly within anchor tags, allowing for the execution of arbitrary scripts in the context of affected users' browsers. The flaw was particularly insidious because it leveraged the very mechanisms designed to allow safe HTML content while simultaneously creating opportunities for code injection.
The operational impact of CVE-2015-6665 extended far beyond simple script execution, as it could enable attackers to perform a wide range of malicious activities against users of vulnerable Drupal installations. Attackers could steal session cookies, redirect users to malicious sites, deface websites, or even gain persistent access to user accounts through session hijacking techniques. The vulnerability was particularly dangerous in environments where administrators relied on the default security configurations of Drupal and the Ctools module, as the flaw was present in widely used components that were not typically subjected to additional security hardening. Organizations running vulnerable systems faced potential data breaches, reputation damage, and compliance violations, especially in sectors requiring strict security controls such as financial services, healthcare, or government agencies. The vulnerability's remote nature meant that attackers could exploit it from anywhere on the internet without requiring physical access to the target systems.
Mitigation strategies for CVE-2015-6665 centered primarily on immediate patching of affected Drupal installations and the Ctools module to their secure versions. Organizations should have implemented comprehensive security monitoring to detect any signs of exploitation attempts and established robust input validation procedures for all user-generated content. The vulnerability highlighted the importance of maintaining current security practices and regularly updating all components within web application frameworks. Security teams should have conducted thorough vulnerability assessments of their Drupal installations to identify any other potentially affected modules or components. Additionally, implementing content security policies and using web application firewalls could have provided additional layers of protection against exploitation attempts, though these measures were secondary to the primary requirement of applying the official patches. The incident underscored the critical need for organizations to maintain up-to-date security practices and to have robust incident response procedures in place for handling such vulnerabilities. This vulnerability aligns with CWE-79, which addresses cross-site scripting flaws, and represents a typical example of how seemingly benign HTML element handling can create security weaknesses that enable sophisticated attacks against web applications.