CVE-2026-90788: MacCMS10 Template Handler RCE Vulnerability

CVE-2026-90788 Overview

CVE-2026-90788 is an OS command injection vulnerability in magicblack MacCMS10 version 2026.1000.4055. The flaw resides in the Template Handler component, specifically in the file /admin1.php/admin/template/index/path/.%40template%40default%40html%40label.html. An authenticated attacker with high privileges can manipulate template path input to inject operating system commands remotely. A public exploit has been released, and the project maintainers were notified through a GitHub issue report but have not yet responded. The vulnerability is classified under CWE-77: Improper Neutralization of Special Elements used in a Command.

Critical Impact
Authenticated remote attackers can execute arbitrary operating system commands on the underlying host through the MacCMS10 template management interface.

Affected Products

magicblack MacCMS10 version 2026.1000.4055
Template Handler component (/admin1.php/admin/template/index/path/)
Deployments where the administrative interface is network-accessible

Discovery Timeline

2026-09-14 - CVE-2026-90788 published to NVD
2026-09-16 - Last updated in NVD database

Technical Details for CVE-2026-90788

Vulnerability Analysis

The vulnerability exists in the MacCMS10 administrative Template Handler. The handler processes a URL-encoded path parameter (.%40template%40default%40html%40label.html) that decodes to a template file identifier. The affected code path fails to neutralize shell metacharacters before passing the user-controlled value to an operating system command execution function.

An attacker who reaches the /admin1.php/admin/template/index/path/ endpoint with valid administrative credentials can supply crafted input that breaks out of the intended template lookup and executes arbitrary shell commands. Because MacCMS10 is a content management system typically deployed on internet-facing web servers, successful exploitation can lead to full compromise of the web application host.

At the time of publication, the upstream project has not acknowledged the GitHub issue #1378, and no vendor patch is available.

Root Cause

The root cause is missing input sanitization in the Template Handler [CWE-77]. User-controlled path segments are concatenated into a command string without escaping, validation, or the use of safe process-execution APIs that separate arguments from the executable.

Attack Vector

Exploitation requires network access to the MacCMS10 admin panel and valid high-privilege credentials. The attacker issues an HTTP request to the vulnerable template path endpoint with shell metacharacters embedded in the URL-encoded path parameter. The server-side handler decodes and passes the payload to an OS command, resulting in remote command execution in the context of the web server process. No user interaction is required beyond the attacker's authenticated request.

Refer to the VulDB entry for CVE-2026-90788 and the MacCMS10 GitHub repository for additional technical context.

Detection Methods for CVE-2026-90788

Indicators of Compromise

HTTP requests to /admin1.php/admin/template/index/path/ containing shell metacharacters such as ;, |, &, backticks, or $(...) in the URL-encoded path
Web server or PHP process spawning unexpected child processes such as sh, bash, cmd.exe, wget, curl, or nc
New or modified files in the MacCMS10 template directory outside of legitimate admin activity
Outbound network connections initiated by the web server process to unknown hosts

Detection Strategies

Inspect web server access logs for requests targeting the template path endpoint with encoded sequences like %40 combined with command-injection characters
Correlate PHP-FPM or Apache/Nginx worker processes with unexpected process creation events on the host
Deploy web application firewall rules that flag command-injection patterns against admin endpoints
Monitor endpoint telemetry for process lineage where the web server user account executes shell interpreters or download utilities

Monitoring Recommendations

Alert on authentication events to the MacCMS10 admin interface from unexpected geolocations or IP ranges
Baseline normal child processes of the web server and alert on deviations
Retain full HTTP request bodies and URIs for admin endpoints to support forensic reconstruction
Enable file integrity monitoring on the MacCMS10 installation directory

How to Mitigate CVE-2026-90788

Immediate Actions Required

Restrict access to the MacCMS10 admin interface using IP allowlisting, VPN, or reverse-proxy authentication until a patch is available
Rotate all administrator credentials and enforce strong, unique passwords with multi-factor authentication where supported
Review web server logs for prior requests to /admin1.php/admin/template/index/path/ with suspicious payloads and investigate any anomalies
Reduce the number of accounts with administrative privileges in MacCMS10 to the minimum required

Patch Information

No official patch has been released by the magicblack MacCMS10 project. The vulnerability was reported through GitHub issue #1378 but has not received a vendor response. Track the MacCMS10 repository for future updates and apply fixes immediately upon release.

Workarounds

Block external access to /admin1.php at the reverse proxy or web application firewall layer
Add WAF signatures that reject requests to the template path endpoint containing shell metacharacters or unexpected URL-encoded sequences
Run the PHP process under a least-privileged user account with no shell access and restricted filesystem permissions
Consider migrating to an alternative CMS if the deployment cannot be adequately isolated while awaiting a vendor fix

bash

# Example Nginx configuration to restrict admin access by source IP
location ~ ^/admin1\.php {
    allow 10.0.0.0/8;      # internal management network
    deny all;
    fastcgi_pass unix:/run/php/php-fpm.sock;
    include fastcgi_params;
}