CVE-2026-27181: MajorDoMo Auth Bypass Vulnerability

CVE-2026-27181 Overview

CVE-2026-27181 is a critical authorization bypass vulnerability in MajorDoMo (Major Domestic Module), an open-source home automation platform. The vulnerability allows unauthenticated attackers to arbitrarily uninstall modules through the market module endpoint, potentially wiping the entire MajorDoMo installation with a series of unauthenticated GET requests. This flaw stems from missing authentication checks in the market module's admin() method, which processes mode parameters directly from user input without verifying credentials.

Critical Impact

An unauthenticated attacker can remotely destroy the entire MajorDoMo home automation system by iterating through module names and triggering the uninstall functionality, leading to complete system unavailability and potential data loss.

Affected Products

• MajorDoMo (Major Domestic Module) - versions prior to the security patch
• MajorDoMo market module component
• Self-hosted MajorDoMo installations exposed to network access

Discovery Timeline

• 2026-02-18 - CVE CVE-2026-27181 published to NVD
• 2026-02-19 - Last updated in NVD database

Technical Details for CVE-2026-27181

Vulnerability Analysis

This vulnerability is classified as CWE-862 (Missing Authorization), a broken access control flaw that allows unauthenticated users to access privileged functionality. The market module in MajorDoMo fails to implement proper authentication checks before processing administrative operations.

The core issue lies in the market module's admin() method, which reads the mode parameter from $_REQUEST via the gr('mode') function and assigns it directly to $this->mode at the start of execution. This design flaw makes all mode-gated code paths, including the critical uninstall mode, reachable without any authentication via the /objects/?module=market endpoint.

When the uninstall mode is triggered, the handler calls uninstallPlugin(), which performs several destructive operations: deleting module records from the database, executing the module's uninstall() method via eval(), recursively deleting the module's directory and template files using removeTree(), and removing associated cycle scripts.

Root Cause

The root cause of CVE-2026-27181 is the complete absence of authentication and authorization checks in the market module's admin() method. The method blindly trusts user-supplied input from $_REQUEST without verifying whether the requesting user has administrative privileges. This architectural flaw violates the principle of least privilege and fails to implement defense-in-depth security controls.

Attack Vector

The attack vector is network-based, requiring no authentication, no user interaction, and presenting low attack complexity. An attacker with network access to a vulnerable MajorDoMo installation can exploit this vulnerability by:

1. Sending a crafted GET request to /objects/?module=market with the mode parameter set to uninstall
2. Specifying a target module name in the request parameters
3. Iterating through known or discovered module names to systematically uninstall all modules

The vulnerability allows attackers to craft simple HTTP GET requests that trigger the uninstall functionality. By enumerating module names and sending repeated requests, an attacker can completely destroy the MajorDoMo installation, removing all installed modules, their configurations, and associated data.

For detailed technical analysis and proof-of-concept information, see the Chocapikk Blog Post and the VulnCheck Security Advisory.

Detection Methods for CVE-2026-27181

Indicators of Compromise

• HTTP GET requests to /objects/?module=market containing mode=uninstall parameter from external or unauthorized IP addresses
• Multiple sequential requests to the market module endpoint with different module name parameters
• Unexpected deletion of module directories under the MajorDoMo installation path
• Database records showing module removals without corresponding administrator activity logs
• Missing or corrupted template files and cycle scripts

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block requests containing mode=uninstall to the /objects/?module=market endpoint
• Monitor HTTP access logs for patterns of unauthenticated requests to administrative endpoints
• Deploy intrusion detection system (IDS) signatures for MajorDoMo-specific attack patterns
• Enable file integrity monitoring on MajorDoMo module directories to detect unauthorized deletions

Monitoring Recommendations

• Configure real-time alerting for any access to the market module's administrative functions from non-trusted networks
• Establish baseline behavior for module installation and uninstallation activities and alert on deviations
• Monitor database transaction logs for unexpected DELETE operations on module-related tables
• Implement network traffic analysis to identify reconnaissance and exploitation attempts targeting MajorDoMo installations

How to Mitigate CVE-2026-27181

Immediate Actions Required

• Restrict network access to MajorDoMo installations using firewall rules, limiting access to trusted IP addresses only
• Place MajorDoMo behind a reverse proxy with authentication requirements for all administrative endpoints
• Create backups of all module configurations, database content, and installation files immediately
• Review access logs for signs of prior exploitation attempts or successful attacks
• Consider temporarily disabling the market module if not actively required

Patch Information

A security patch addressing this vulnerability is available via GitHub Pull Request #1177. Organizations running MajorDoMo should apply this patch immediately or update to a version that includes the fix. The patch adds proper authentication checks to the market module's admin() method, ensuring that only authenticated administrators can access mode-gated functionality.

For additional context and technical details, refer to the VulnCheck Security Advisory.

Workarounds

• Implement network-level access controls to restrict access to the MajorDoMo web interface to trusted networks only
• Deploy a reverse proxy (such as nginx or Apache) with HTTP Basic Authentication in front of MajorDoMo to enforce authentication on all requests
• Use web application firewall rules to block requests containing mode=uninstall or similar administrative parameters to the market endpoint
• If feasible, disable or remove the market module entirely until a patch can be applied

# Example: Restrict MajorDoMo access using iptables
# Allow only trusted network (e.g., 192.168.1.0/24) to access MajorDoMo on port 80
iptables -A INPUT -p tcp --dport 80 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP