CVE-2024-3277 in Yumpu ePaper Publishing Plugin
Summary
by MITRE • 05/30/2024
The Yumpu ePaper publishing plugin for WordPress is vulnerable to unauthorized modification of data due to a missing capability check on the ajax_handler function in all versions up to, and including, 2.0.24. This makes it possible for authenticated attackers, with subscriber-level access and above, to upload PDF files and publish them, as well as modify the API key.
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Analysis
by VulDB Data Team • 05/30/2024
The Yumpu ePaper publishing plugin for WordPress presents a critical authorization vulnerability that stems from inadequate capability validation within its ajax_handler function. This flaw affects all versions up to and including 2.0.24, creating a pathway for authenticated attackers who possess subscriber-level privileges or higher to execute unauthorized modifications to the plugin's functionality. The vulnerability specifically arises from the absence of proper access control checks that should validate user permissions before allowing sensitive operations to proceed. Attackers with minimal privileges can exploit this weakness to upload PDF files directly through the plugin interface and subsequently publish them, effectively bypassing normal content approval workflows that typically require higher privilege levels.
The technical implementation of this vulnerability lies in the ajax_handler function's failure to verify whether the requesting user possesses sufficient capabilities before processing file upload and API key modification requests. This missing capability check represents a direct violation of secure coding principles and constitutes a classic example of insufficient authorization checks as classified under CWE-863. The flaw allows attackers to manipulate the plugin's behavior by leveraging their existing authenticated session, which undermines the principle of least privilege that should govern all user interactions with web application components. When an authenticated user with subscriber-level access attempts to perform actions through the ajax interface, the system fails to validate whether this user has the appropriate permissions to execute such operations.
The operational impact of this vulnerability extends beyond simple data modification to encompass potential content injection and configuration manipulation within the WordPress environment. An attacker can upload malicious PDF files that may contain embedded exploits or links to malicious resources, creating a vector for further attacks on the WordPress installation or its users. Additionally, the ability to modify API keys allows attackers to potentially redirect the plugin's functionality to external services controlled by the attacker, enabling data exfiltration or manipulation of the published content. This vulnerability also creates opportunities for attackers to disrupt normal publishing workflows and potentially gain unauthorized access to premium Yumpu services through misuse of legitimate API credentials.
Security practitioners should consider this vulnerability in relation to the attack tactics outlined in the MITRE ATT&CK framework, particularly under the privilege escalation and persistence categories. The vulnerability enables attackers to move laterally within the WordPress environment by leveraging their authenticated session to perform operations that should typically require administrator-level privileges. Organizations using this plugin should immediately implement mitigations including updating to the latest version where the capability check has been implemented, reviewing user permissions to ensure appropriate access levels are enforced, and monitoring for unauthorized file uploads or API key modifications. The vulnerability also highlights the importance of implementing comprehensive input validation and access control mechanisms within all AJAX handlers, as these interfaces often serve as attack vectors due to their direct interaction with backend processes without traditional authentication barriers.
The remediation approach should focus on implementing proper capability checks within the ajax_handler function to validate that users possess appropriate permissions before allowing file uploads or configuration changes. This includes verifying user roles and capabilities against expected privilege levels for each operation, implementing rate limiting for upload operations to prevent abuse, and ensuring that API key modifications require explicit administrative approval. Organizations should also conduct regular security assessments of their WordPress plugins to identify similar authorization flaws that may exist in other third-party components. The vulnerability serves as a reminder of the critical importance of access control validation within web applications, particularly when dealing with file upload functionality and configuration management interfaces.