CVE-2021-33484 in Comments Pro
Summary
by MITRE • 09/07/2021
An issue was discovered in CommentsService.ashx in OnyakTech Comments Pro 3.8. An attacker can download a copy of the installer, decompile it, and discover a hardcoded IV used to encrypt the username and userid in the comment POST request. Additionally, the attacker can decrypt the encrypted encryption key (sent as a parameter in the comment form request) by setting this encrypted value as the username, which will appear on the comment page in its decrypted form. Using these two values (combined with the encryption functionality discovered in the decompiled installer), the attacker can encrypt another user's ID and username. These values can be used as part of the comment posting request in order to spoof the user.
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Analysis
by VulDB Data Team • 09/10/2021
The vulnerability described in CVE-2021-33484 represents a critical cryptographic weakness in the CommentsService.ashx component of OnyakTech Comments Pro version 3.8. This flaw stems from the improper implementation of encryption mechanisms within the comment submission process, creating multiple attack vectors that collectively enable user identity spoofing. The vulnerability manifests through the exposure of hardcoded initialization vectors and encryption keys that are embedded within the application's installer, which can be readily accessed through simple decompilation techniques. This represents a fundamental failure in cryptographic implementation practices and violates established security principles for secure key management.
The technical exploitation of this vulnerability begins with the attacker's ability to download and decompile the application installer, where they discover a hardcoded initialization vector that is used to encrypt sensitive user data during comment submission. This hardcoded IV creates a predictable encryption pattern that significantly weakens the overall cryptographic security of the system. Additionally, the attacker can exploit the encryption key used for encrypting the username and userid fields, which is also discoverable through decompilation. The vulnerability allows for a specific decryption technique where an attacker can set the encrypted encryption key as a username parameter, causing the system to display the decrypted value on the comment page. This creates a direct information disclosure vulnerability that exposes the underlying encryption keys and methods used by the system.
The operational impact of this vulnerability extends beyond simple information disclosure to enable full user identity spoofing capabilities. Once an attacker has obtained both the hardcoded IV and the encryption key through decompilation, they can construct encrypted user identifiers and usernames that will be accepted by the system as legitimate. This allows the attacker to post comments as any user within the system, potentially enabling them to post malicious content, manipulate discussions, or conduct social engineering attacks. The vulnerability effectively undermines the authentication and authorization mechanisms of the comment system, creating a persistent threat that can be exploited repeatedly. This type of vulnerability is particularly concerning as it allows for long-term unauthorized access and manipulation of user-generated content within the application.
The security implications of CVE-2021-33484 align with CWE-310, which addresses cryptographic weaknesses and improper key management practices. The vulnerability demonstrates poor implementation of encryption standards and violates fundamental security principles regarding key storage and management. From an attack perspective, this vulnerability maps to several ATT&CK techniques including T1566 for social engineering and T1071 for application layer protocol usage. The attack chain follows T1071.004 for application layer protocol data encoding and T1566.001 for credential harvesting through social engineering, as the attacker can effectively impersonate legitimate users through the comment system. The vulnerability also relates to T1528 for stolen credentials and T1046 for network service scanning, as the attacker can systematically test and exploit the encryption mechanisms. Organizations should immediately implement mitigations including removing hardcoded cryptographic values, implementing proper key rotation mechanisms, and employing secure encryption practices that do not rely on embedded secrets. The vulnerability highlights the importance of secure code review processes and the need for comprehensive security testing, particularly for applications that handle user authentication and authorization through web-based interfaces.