CVE-2014-9117 in MantisBT
Summary
by MITRE
MantisBT before 1.2.18 uses the public_key parameter value as the key to the CAPTCHA answer, which allows remote attackers to bypass the CAPTCHA protection mechanism by leveraging knowledge of a CAPTCHA answer for a public_key parameter value, as demonstrated by E4652 for the public_key value 0.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 04/07/2022
The vulnerability identified as CVE-2014-9117 affects MantisBT versions prior to 1.2.18 and represents a critical weakness in the web application's CAPTCHA implementation. This flaw stems from the improper handling of cryptographic keys within the CAPTCHA validation process, where the public_key parameter value directly serves as the cryptographic key for validating CAPTCHA responses. The security mechanism was designed to prevent automated bot submissions by requiring users to correctly input visual CAPTCHA text, but this design flaw fundamentally undermines the protection by creating a predictable relationship between the public key and the expected CAPTCHA answer.
The technical exploitation of this vulnerability occurs through a straightforward yet effective approach that leverages the predictable nature of the CAPTCHA key generation. Attackers can observe or derive the correct CAPTCHA answer for a given public_key value by examining the application's behavior or through prior knowledge of the system's internal key derivation process. The specific demonstration of this vulnerability using the public_key value 0 indicates that the system uses a deterministic algorithm where the key value directly maps to a known CAPTCHA answer, effectively eliminating the security benefit of the CAPTCHA mechanism. This vulnerability falls under the CWE-310 category of Cryptographic Issues, specifically addressing weaknesses in key management and cryptographic implementation.
The operational impact of this vulnerability extends far beyond simple bypass of CAPTCHA protection, creating potential for widespread abuse in automated attack scenarios. Attackers can exploit this weakness to submit spam comments, create fraudulent user accounts, or perform denial-of-service attacks through automated submissions that would normally be blocked by CAPTCHA validation. The vulnerability effectively neutralizes the CAPTCHA protection entirely, allowing malicious actors to flood systems with unwanted content or abuse service resources without any human verification. This represents a significant degradation in the application's security posture and can lead to reputation damage, increased server load, and potential data integrity issues.
Organizations affected by this vulnerability should immediately implement the patch available for MantisBT version 1.2.18 or later, which corrects the CAPTCHA implementation by removing the direct dependency between the public_key parameter and the cryptographic key used for validation. The mitigation strategy should also include monitoring for suspicious activity patterns that might indicate exploitation attempts and implementing additional layers of protection such as rate limiting or IP-based restrictions. From a defensive perspective, this vulnerability demonstrates the importance of proper cryptographic key management and the principle of not using predictable values as cryptographic keys. The ATT&CK framework categorizes this as a technique related to credential access and privilege escalation through the exploitation of weak authentication mechanisms, emphasizing the need for robust validation processes and proper input sanitization in web applications.