CVE-2008-2019 in SMF
Summary
by MITRE
Simple Machines Forum (SMF), probably 1.1.4, relies on "randomly generated static" to hinder brute-force attacks on the WAV file (aka audio) CAPTCHA, which allows remote attackers to pass the CAPTCHA test via an automated attack that considers Hamming distances. NOTE: this issue reportedly exists because of an insufficient fix for CVE-2007-3308.
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Analysis
by VulDB Data Team • 09/23/2018
The vulnerability identified as CVE-2008-2019 affects Simple Machines Forum version 1.1.4 and represents a critical weakness in the forum's CAPTCHA implementation that undermines security measures designed to prevent automated attacks. This issue specifically targets the audio CAPTCHA system that was intended to provide an alternative authentication method for users who cannot read standard text CAPTCHAs, yet the implementation contains a fundamental flaw that renders the security mechanism ineffective. The vulnerability stems from the forum's reliance on what appears to be randomly generated static in the WAV file generation process, which creates predictable patterns that can be exploited by malicious actors.
The technical flaw in this vulnerability lies in the insufficient randomness of the audio CAPTCHA generation algorithm, which allows attackers to analyze the Hamming distances between different audio samples and systematically bypass the authentication mechanism. This approach exploits the mathematical properties of the audio signal processing to determine the correct CAPTCHA response without requiring human intervention or extensive brute-force computation. The vulnerability specifically targets the audio CAPTCHA component, which uses audio files to verify user identity, making it particularly concerning for forums that rely heavily on automated registration processes or those that are susceptible to spam bot attacks. The implementation fails to properly randomize the audio signal generation, creating predictable patterns that can be reverse-engineered through statistical analysis.
The operational impact of this vulnerability is significant as it allows remote attackers to bypass the CAPTCHA protection mechanism entirely, potentially enabling automated account creation, spam posting, and other malicious activities that the CAPTCHA system was specifically designed to prevent. This weakness directly undermines the forum's security posture and could lead to widespread abuse of the platform, including the creation of fake accounts, posting of spam content, and potential exploitation of other vulnerabilities through automated means. The vulnerability is particularly dangerous because it allows attackers to circumvent authentication measures without requiring sophisticated tools or extensive computational resources, making it accessible to a broad range of threat actors. The issue represents a regression in security measures, as it stems from an insufficient fix for a previous vulnerability CVE-2007-3308, indicating that the security improvements were inadequate and failed to address the core randomness problem.
The security implications extend beyond simple CAPTCHA bypassing, as this vulnerability could enable more sophisticated attacks that leverage the compromised authentication system to gain unauthorized access to user accounts or to launch further attacks against the forum infrastructure. Organizations using SMF version 1.1.4 should consider this vulnerability as a critical security concern that requires immediate attention and remediation. The flaw demonstrates poor understanding of cryptographic principles and randomness requirements for security-critical components, which aligns with CWE-330, which addresses insufficient randomness in security-critical applications. This vulnerability also relates to ATT&CK technique T1110, which covers credential access through brute force or password guessing, as the CAPTCHA bypass allows automated credential testing that would otherwise be prevented by proper authentication mechanisms. The vulnerability highlights the importance of proper entropy and randomness in security implementations, particularly for authentication systems that are meant to prevent automated attacks and maintain system integrity.