CVE-2016-8600 in dotCMS
Summary
by MITRE
In dotCMS 3.2.1, attacker can load captcha once, fill it with correct value and then this correct value is ok for forms with captcha check later.
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Analysis
by VulDB Data Team • 05/14/2019
The vulnerability identified as CVE-2016-8600 affects dotCMS version 3.2.1 and represents a critical flaw in the content management system's CAPTCHA implementation. This issue stems from improper session management and validation logic within the CAPTCHA verification mechanism, allowing attackers to exploit a race condition or state inconsistency in the verification process. The flaw specifically manifests when an attacker successfully loads a CAPTCHA image, correctly inputs the CAPTCHA value, and then subsequently uses that same correct value to bypass CAPTCHA checks on multiple forms within the same session or across different sessions.
The technical root cause of this vulnerability lies in the inadequate handling of CAPTCHA state persistence and validation. When a CAPTCHA image is generated and validated, the system should maintain a strict one-time use policy where each CAPTCHA value is invalidated immediately upon successful validation. However, in dotCMS 3.2.1, the validation process fails to properly invalidate the CAPTCHA value after its initial successful use, creating a window where the same CAPTCHA response can be reused multiple times. This represents a failure in the principle of least privilege and proper state management, which are fundamental security concepts that align with CWE-697, which deals with incorrect comparison of different types of data. The vulnerability essentially creates a persistent authentication bypass mechanism that undermines the entire purpose of CAPTCHA as a security control.
The operational impact of this vulnerability is significant as it allows attackers to circumvent automated form protection mechanisms that are designed to prevent spam, brute force attacks, and automated data scraping. An attacker can exploit this weakness to submit multiple forms without re-entering CAPTCHA values, effectively bypassing rate limiting and anti-spam measures that are crucial for protecting web applications from abuse. This vulnerability particularly affects forms that rely on CAPTCHA for user authentication, content submission, and registration processes, making it a serious concern for any organization using dotCMS for public-facing applications. The attack vector is relatively simple and does not require advanced technical skills, making it accessible to a broad range of threat actors and increasing the potential for widespread exploitation.
Security mitigations for this vulnerability should focus on implementing proper CAPTCHA state management and validation protocols. Organizations should immediately upgrade to a patched version of dotCMS that addresses the CAPTCHA validation logic, ensuring that each CAPTCHA value is invalidated upon successful use. The implementation should follow secure coding practices that align with the OWASP Top Ten security controls, particularly those related to input validation and session management. Additionally, administrators should implement additional layers of protection such as rate limiting, IP-based restrictions, and behavioral analysis to detect and prevent automated abuse patterns. The fix should ensure that CAPTCHA tokens are properly scoped to individual form submissions and that the validation system maintains proper state tracking to prevent reuse of previously validated CAPTCHA values. This vulnerability highlights the importance of proper session management and input validation in web applications, which are core requirements of the NIST Cybersecurity Framework and align with ATT&CK technique T1110 for Brute Force and T1078 for Valid Accounts to prevent unauthorized access and automated exploitation.