CVE-2026-15516: MacCMS Pro Auth Bypass Vulnerability

CVE-2026-15516 Overview

CVE-2026-15516 is an authorization bypass vulnerability in MacCMS Pro up to version 2022.1000.3005. The flaw resides in the step5 function of application/install/controller/Index.php, part of the Installation Module. Attackers can manipulate the installation workflow to bypass authorization controls remotely without prior authentication. Public exploit details are available, though successful exploitation requires high attack complexity. The MacCMS project addressed the issue in release v2022.1000.3025.

Critical Impact
Remote attackers can bypass authorization on the MacCMS Pro installation endpoint, potentially altering installation state and gaining unauthorized access to configuration functions.

Affected Products

MacCMS Pro versions up to and including 2022.1000.3005
Component: Installation Module (application/install/controller/Index.php)
Fixed in: MacCMS Pro 2022.1000.3025

Discovery Timeline

2026-07-13 - CVE-2026-15516 published to the National Vulnerability Database (NVD)
2026-07-13 - Last updated in NVD database

Technical Details for CVE-2026-15516

Vulnerability Analysis

The vulnerability is classified as an improper authorization flaw [CWE-285] in the MacCMS Pro content management system. The step5 function within the installation controller fails to validate whether the caller is authorized to invoke installation logic. Because the installer route remains reachable after initial setup, a remote attacker can send crafted HTTP requests to reach the function and manipulate the installation state. The attack requires no authentication and no user interaction, but exploitation complexity is rated high, indicating conditions outside the attacker's direct control must be met to succeed. Public disclosure of exploit details raises the likelihood of opportunistic scanning against exposed MacCMS deployments.

Root Cause

The step5 handler in application/install/controller/Index.php does not enforce a check confirming that installation has not already completed, nor does it verify caller authorization. Installation controllers in production deployments should be disabled, gated by a lock file, or restricted to trusted networks. The absence of these guardrails allows the endpoint to accept unauthenticated requests that would normally only occur during first-time setup.

Attack Vector

Exploitation occurs over the network against the exposed MacCMS Pro web interface. An attacker issues HTTP requests directly to the installation endpoint hosting the vulnerable step5 function. Successful requests bypass authorization and interact with installation logic. No verified public proof-of-concept code is republished here; refer to the VulDB entry for CVE-2026-15516 and the maintainer's release notes for technical context.

Detection Methods for CVE-2026-15516

Indicators of Compromise

HTTP requests targeting application/install/controller/Index.php or install routes such as /install/index/step5 after the CMS is already provisioned.
Unexpected modifications to MacCMS configuration files or the site database following anonymous requests to installer paths.
Web server access logs showing requests to installer endpoints from external IP addresses.

Detection Strategies

Deploy web application firewall (WAF) rules that block or alert on requests to /install/ paths in production environments.
Review application logs for calls to the step5 function originating from untrusted networks or after initial deployment.
Baseline expected traffic to MacCMS administrative and installation URIs, then alert on deviations.

Monitoring Recommendations

Correlate web server telemetry with file integrity monitoring on the MacCMS installation directory.
Track outbound connections from the MacCMS host that follow requests to installer endpoints, which may indicate follow-on activity.
Aggregate CMS access logs into a centralized logging platform for retrospective hunting against installer URI patterns.

How to Mitigate CVE-2026-15516

Immediate Actions Required

Upgrade MacCMS Pro to version 2022.1000.3025 or later, as recommended by the maintainer.
Remove or restrict access to the application/install/ directory on production installations that no longer require the installer.
Restrict inbound access to the MacCMS management interface using network access control lists or reverse-proxy authentication.

Patch Information

The MacCMS project released version 2022.1000.3025 to remediate the authorization bypass in step5. Release artifacts are available on the MacCMS10 GitHub releases page. Administrators should validate the upgrade in a staging environment before rolling it into production, and confirm that installer files are removed post-upgrade.

Workarounds

Delete or rename the application/install/ directory once the CMS is fully provisioned to prevent installer routes from being reached.
Block requests to installer URIs at the web server or WAF layer until the upgrade is applied.
Place the MacCMS site behind an authenticating reverse proxy or VPN during any maintenance window that requires access to installation logic.

bash

# Example nginx rule to block installer paths in production
location ~* ^/install/ {
    return 404;
}