CVE-2025-26776: Chaty Pro RCE Vulnerability

CVE-2025-26776 Overview

CVE-2025-26776 is a critical unrestricted file upload vulnerability affecting the Chaty Pro WordPress plugin. This flaw allows unauthenticated attackers to upload arbitrary files with dangerous types, including web shells, directly to vulnerable web servers. The vulnerability stems from improper validation of file types during the upload process, enabling complete server compromise without requiring any authentication or user interaction.

Critical Impact

Unauthenticated attackers can upload web shells to gain complete control over affected WordPress installations, leading to data theft, site defacement, malware distribution, and lateral movement within the hosting environment.

Affected Products

• Chaty Pro WordPress Plugin versions up to and including 3.3.3
• WordPress installations running vulnerable Chaty Pro versions
• Web servers hosting affected WordPress sites

Discovery Timeline

• 2025-02-22 - CVE-2025-26776 published to NVD
• 2025-02-22 - Last updated in NVD database

Technical Details for CVE-2025-26776

Vulnerability Analysis

This vulnerability is classified as CWE-434 (Unrestricted Upload of File with Dangerous Type), representing a fundamental failure in input validation within the Chaty Pro plugin's file upload functionality. The plugin fails to properly restrict the types of files that can be uploaded through its interface, allowing malicious actors to bypass intended security controls and upload executable server-side scripts.

The vulnerability enables attackers operating remotely over the network to exploit the flaw with low complexity. No privileges or user interaction are required, making this vulnerability particularly dangerous in internet-facing WordPress deployments. Successful exploitation affects resources beyond the vulnerable component's security scope, potentially compromising the entire hosting environment.

Root Cause

The root cause of CVE-2025-26776 lies in the absence of proper file type validation and sanitization in the Chaty Pro plugin's upload handling code. The vulnerable versions through 3.3.3 accept file uploads without adequately verifying:

• File extension against an allowlist of safe types
• MIME type validation to prevent content-type spoofing
• File content inspection to detect malicious payloads
• Proper storage location restrictions to prevent execution of uploaded files

This allows attackers to upload PHP files or other server-executable scripts that the web server will process upon request.

Attack Vector

The attack vector for this vulnerability is network-based and requires no authentication. An attacker can exploit this flaw by:

1. Identifying a WordPress site running a vulnerable version of Chaty Pro (versions through 3.3.3)
2. Crafting a malicious HTTP request containing a web shell payload disguised or directly uploaded as an executable file
3. Submitting the upload request to the vulnerable endpoint without authentication
4. Accessing the uploaded web shell via direct URL to execute arbitrary commands on the server

The exploitation is straightforward as no privileges, user interaction, or complex attack chains are required. Once a web shell is uploaded, the attacker gains persistent access to execute system commands, read/write files, establish reverse shells, and pivot to other systems.

Detection Methods for CVE-2025-26776

Indicators of Compromise

• Unexpected PHP files or files with double extensions (e.g., image.php.jpg) appearing in WordPress upload directories
• Presence of common web shell signatures such as eval(), base64_decode(), system(), or passthru() in newly created files
• Suspicious outbound network connections originating from the web server process
• Unusual file creation timestamps in wp-content/uploads/ or plugin-specific directories

Detection Strategies

• Implement file integrity monitoring (FIM) on WordPress directories to detect unauthorized file additions
• Deploy web application firewall (WAF) rules to inspect and block malicious file upload attempts
• Enable detailed logging of HTTP POST requests to upload endpoints for forensic analysis
• Utilize endpoint detection solutions like SentinelOne to identify and block web shell execution attempts

Monitoring Recommendations

• Monitor web server access logs for requests to unusual file paths within upload directories
• Configure alerts for PHP process spawning shell commands (/bin/sh, /bin/bash, cmd.exe)
• Track WordPress plugin version inventory and flag instances running Chaty Pro 3.3.3 or earlier
• Review server-side execution of files in upload directories as a critical security indicator

How to Mitigate CVE-2025-26776

Immediate Actions Required

• Update Chaty Pro plugin to the latest patched version immediately
• Audit all files in WordPress upload directories for suspicious or unexpected executable files
• Review web server access logs for signs of exploitation attempts targeting upload functionality
• Temporarily disable the Chaty Pro plugin if an update is not immediately available

Patch Information

Users should update the Chaty Pro WordPress plugin to a version newer than 3.3.3 that addresses this vulnerability. Refer to the Patchstack security advisory for detailed patch information and update guidance. WordPress administrators should verify the update has been applied and confirm no malicious files were uploaded prior to patching.

Workarounds

• Configure web server to deny execution of PHP files within upload directories using server configuration rules
• Implement strict file type allowlisting at the web application firewall level
• Restrict upload directory permissions to prevent script execution
• Deploy runtime application self-protection (RASP) solutions to block web shell execution

# Apache configuration to prevent PHP execution in uploads directory
# Add to .htaccess in wp-content/uploads/
<FilesMatch "\.php$">
    Deny from all
</FilesMatch>

# Nginx configuration equivalent
# Add within the appropriate server block
location ~* /wp-content/uploads/.*\.php$ {
    deny all;
}