CVE-2026-82901 in Ultra Addons for Contact Form 7 Plugin
Summary
by MITRE • 09/26/2026
The Ultra Addons for Contact Form 7 plugin for WordPress is vulnerable to Arbitrary File Upload due to insufficient file type validation in the 'uacf7_wpcf7_mail_components' function in all versions up to, and including, 3.5.50. This makes it possible for unauthenticated attackers to upload arbitrary files on the affected site's server which may make remote code execution possible. Note: This is only exploitable when the plugin's PDF Generator module is enabled, which is disabled by default.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 09/26/2026
The Ultra Addons for Contact Form 7 WordPress plugin contains a critical security vulnerability classified as an Arbitrary File Upload flaw within its core functionality. Specifically, this weakness resides in the uacf7_wpcf7_mail_components function and affects all versions up to and including 3.5.50. The root cause of this issue is insufficient validation of file types during the upload process. In a secure implementation, server-side checks must rigorously verify that uploaded files conform to expected formats, extensions, and content signatures before being saved to the filesystem. However, in this vulnerable version, the plugin fails to enforce these constraints adequately, allowing attackers to bypass standard security controls designed to prevent malicious file ingestion.
This vulnerability is categorized under CWE-434, which describes an unrestricted upload of a file with dangerous type. From a threat actor perspective, this aligns with MITRE ATT&CK technique T1505.003, known as Web Shell: ASPX, or more broadly T1505 Server Software Component, where adversaries install web shells to maintain persistent access and execute commands on the target system. The ability to upload arbitrary files is particularly severe because it often serves as a precursor to Remote Code Execution (RCE). Once an attacker successfully uploads a malicious script file, such as a PHP shell or ASPX payload, they can interact with that file via HTTP requests to gain full control over the web server environment.
It is important to note specific operational constraints regarding this vulnerability's exploitability. The flaw is only exploitable when the plugin's PDF Generator module is enabled on the target WordPress site. By default, this module is disabled in standard installations, which means that many sites remain unaffected unless an administrator has explicitly activated this feature. This dependency creates a conditional attack surface where the risk is present but not universally active across all deployments of the software. Attackers targeting such environments must first identify whether the PDF Generator component is operational before attempting to leverage the file upload flaw for further exploitation.
The potential impact of successful exploitation includes complete compromise of the underlying web server, unauthorized access to sensitive data stored within the WordPress database, and the ability to pivot into other systems on the internal network if the server has broader connectivity privileges. Attackers may use this foothold to deploy ransomware, deface websites, or establish backdoors for long-term persistence without detection by standard security monitoring tools that do not inspect file upload behaviors closely enough.
To mitigate this risk, administrators should immediately update the Ultra Addons for Contact Form 7 plugin to a version newer than 3.5.50 where these validation checks have been corrected and hardened against bypass techniques. If updating is not immediately feasible due to compatibility concerns with other site components, it is critical to ensure that the PDF Generator module remains disabled unless absolutely necessary for business operations. Additionally, implementing Web Application Firewall rules can help detect and block suspicious file upload attempts by monitoring for unusual MIME types or executable extensions being submitted through contact form endpoints. Regular security audits and adherence to least privilege principles in server configurations further reduce the blast radius should a vulnerability be exploited.