CVE-2024-40761 in Answer
Summary
by MITRE • 09/25/2024
Inadequate Encryption Strength vulnerability in Apache Answer.
This issue affects Apache Answer: through 1.3.5.
Using the MD5 value of a user's email to access Gravatar is insecure and can lead to the leakage of user email. The official recommendation is to use SHA256 instead. Users are recommended to upgrade to version 1.4.0, which fixes the issue.
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Analysis
by VulDB Data Team • 07/11/2025
The inadequate encryption strength vulnerability in Apache Answer represents a significant security weakness that exposes user privacy through insecure hashing practices. This vulnerability affects versions through 1.3.5 and specifically targets the method used to generate Gravatar URLs for user avatars. The system incorrectly utilizes MD5 hashing of user email addresses to create Gravatar identifiers, which creates a dangerous attack surface that can be exploited by malicious actors. The fundamental flaw lies in the choice of cryptographic hash function, as MD5 is widely recognized as cryptographically broken and unsuitable for security-sensitive applications. This weakness enables potential attackers to perform rainbow table attacks or exploit known MD5 collisions to reverse engineer user email addresses from the publicly accessible Gravatar URLs.
The operational impact of this vulnerability extends beyond simple privacy concerns to encompass potential account takeover scenarios and user data exposure. When user email addresses are derived from MD5 hashes, attackers can leverage precomputed hash tables or perform brute force attacks to discover the original email addresses associated with specific Gravatar identifiers. This creates a direct pathway for phishing attacks, social engineering campaigns, and credential stuffing attacks against users. The vulnerability directly violates security best practices outlined in industry standards such as CWE-327, which specifically addresses the use of weak cryptographic algorithms, and aligns with ATT&CK technique T1589.003 for credential access through social engineering. The exposure of user email addresses through this mechanism undermines the confidentiality of user data and creates cascading security risks throughout the application ecosystem.
The recommended mitigation strategy involves upgrading to version 1.4.0, which properly implements SHA256 hashing for Gravatar URL generation. This upgrade addresses the core cryptographic weakness by employing a robust, collision-resistant hash function that provides adequate security for the intended purpose. The transition from MD5 to SHA256 represents a fundamental improvement that aligns with NIST guidelines for cryptographic hash functions and ensures compliance with modern security standards. Organizations utilizing Apache Answer should prioritize this upgrade as an immediate security measure, while also considering additional defensive strategies such as monitoring for suspicious Gravatar access patterns and implementing rate limiting for avatar requests. The fix demonstrates proper security engineering practices by moving away from deprecated cryptographic algorithms and toward industry-approved alternatives that provide sufficient entropy and resistance to various attack vectors. This vulnerability serves as a reminder of the critical importance of cryptographic hygiene in web applications and the potential consequences of using insecure hashing algorithms for user identification purposes.