CVE-2007-0658 in Drupal
Summary
by MITRE
The (1) Textimage 4.7.x before 4.7-1.2 and 5.x before 5.x-1.1 module for Drupal and the (2) Captcha 4.7.x before 4.7-1.2 and 5.x before 5.x-1.1 module for Drupal allow remote attackers to bypass the CAPTCHA test via an empty captcha element in $_SESSION.
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Analysis
by VulDB Data Team • 08/08/2022
The vulnerability described in CVE-2007-0658 represents a critical security flaw in Drupal's CAPTCHA implementation that affects multiple versions of both the Textimage and Captcha modules. This issue stems from improper validation of CAPTCHA elements within the session management system, creating a pathway for attackers to circumvent security controls designed to prevent automated submissions and spam attacks. The vulnerability specifically targets the session-based CAPTCHA verification mechanism that was widely deployed across Drupal installations to protect contact forms, user registration pages, and other sensitive submission points from bot-driven abuse.
The technical root cause of this vulnerability lies in the flawed session handling logic where the system fails to properly validate whether a CAPTCHA element exists in the $_SESSION array before accepting the verification result. Attackers can exploit this by manipulating the session data to include an empty or null captcha element, effectively bypassing the CAPTCHA validation process entirely. This allows malicious actors to submit forms without completing the required visual or audio CAPTCHA challenge, undermining the entire security mechanism that these modules were designed to enforce. The vulnerability is particularly dangerous because it operates at the session management level, making it difficult to detect through standard input validation measures.
The operational impact of this vulnerability extends beyond simple bypass of CAPTCHA mechanisms to potentially enable widespread automated attacks against Drupal websites. Attackers can leverage this weakness to flood contact forms with spam submissions, perform brute force attacks on user registration systems, or exploit other CAPTCHA-protected functionality to gain unauthorized access to sensitive areas of the website. This vulnerability directly violates security principles related to input validation and session integrity, as defined in CWE-20 for improper input validation and CWE-345 for insufficient verification of data integrity. The attack vector is particularly concerning because it requires minimal technical expertise and can be automated, making it attractive to both script kiddies and organized attack groups.
Mitigation strategies for this vulnerability should focus on immediate patching of affected modules to version 4.7-1.2 or 5.x-1.1 respectively, along with implementing additional defensive measures such as enhanced session validation, rate limiting on form submissions, and monitoring for unusual patterns of CAPTCHA bypass attempts. Organizations should also consider implementing web application firewalls to detect and block suspicious session manipulation attempts, while ensuring that all CAPTCHA implementations follow proper session management practices as outlined in industry standards. The vulnerability demonstrates the critical importance of proper session validation and input sanitization in web applications, aligning with ATT&CK techniques related to credential access and privilege escalation through session manipulation. Regular security audits of session management components and comprehensive testing of CAPTCHA implementations should become standard practice to prevent similar vulnerabilities from emerging in future deployments.