CVE-2026-3867: Moxa Secure Router Information Disclosure

CVE-2026-3867 Overview

An improper ownership management vulnerability has been identified in Moxa's Secure Router. This vulnerability allows a low-privileged authenticated user to access a configuration file containing the hashed password of the administrative account. Successful exploitation could enable an attacker to obtain sensitive information, potentially leading to further compromise of the affected device.

Critical Impact

A low-privileged user can access administrative password hashes from exported configuration files, enabling offline password cracking attacks against administrative accounts.

Affected Products

• Moxa Secure Router (specific models detailed in vendor advisory)

Discovery Timeline

• 2026-04-27 - CVE-2026-3867 published to NVD
• 2026-04-27 - Last updated in NVD database

Technical Details for CVE-2026-3867

Vulnerability Analysis

This vulnerability is classified as CWE-282 (Improper Ownership Management), indicating a flaw in how the affected Moxa Secure Router manages file ownership and access permissions. The core issue lies in the improper handling of configuration file permissions, which allows users with low-level privileges to read sensitive data that should be restricted to administrative accounts only.

The vulnerability has a notable precondition for exploitation: the configuration file must have been previously exported. This constraint limits the attack surface but does not eliminate the risk, particularly in environments where configuration backups are routinely performed or stored in accessible locations.

Importantly, this vulnerability only affects confidentiality—there is no impact on integrity or availability of the affected product, and no downstream impact has been identified on connected systems.

Root Cause

The root cause of this vulnerability stems from improper ownership management mechanisms within the Moxa Secure Router's file system. When configuration files are exported, the ownership and permission settings are not properly enforced, allowing users with insufficient privileges to access these files. The configuration export process fails to apply appropriate access controls, leaving sensitive data such as administrative password hashes exposed to lower-privileged users.

Attack Vector

The attack vector for CVE-2026-3867 is network-based, requiring low-level authentication to the device. An attacker would need to:

1. Gain authenticated access to the Moxa Secure Router with a low-privileged account
2. Wait for or trigger a configuration file export operation
3. Access the exported configuration file containing the hashed administrative password
4. Perform offline password cracking attacks against the captured hash

The vulnerability mechanism involves improper file permission handling during configuration export operations. When a configuration file is exported, the access control mechanisms fail to restrict read access to administrative users only, allowing any authenticated user to potentially retrieve sensitive credential data.

For technical details regarding the specific vulnerable components and exploitation mechanics, refer to the Moxa Security Advisory MPSA-261521.

Detection Methods for CVE-2026-3867

Indicators of Compromise

• Unexpected access to configuration files by non-administrative user accounts
• Anomalous file system access patterns targeting exported configuration directories
• Suspicious authentication attempts using previously unknown credentials after configuration exports
• Evidence of password cracking tools or hash extraction activity on the network

Detection Strategies

• Monitor file access logs for configuration file reads by low-privileged accounts
• Implement audit logging for all configuration export operations
• Deploy file integrity monitoring on configuration storage directories
• Review authentication logs for privilege escalation attempts following configuration exports

Monitoring Recommendations

• Enable verbose logging on Moxa Secure Router devices to capture file access events
• Configure SIEM rules to alert on configuration file access by non-administrative users
• Implement network traffic analysis to detect exfiltration of configuration data
• Establish baseline user behavior patterns to identify anomalous access attempts

How to Mitigate CVE-2026-3867

Immediate Actions Required

• Review and restrict user accounts with access to Moxa Secure Router devices
• Audit recent configuration export operations and verify the security of exported files
• Implement the principle of least privilege for all device accounts
• Securely delete or protect any previously exported configuration files

Patch Information

Moxa has released security guidance addressing this vulnerability. Administrators should consult the Moxa Security Advisory MPSA-261521 for the latest firmware updates and patching instructions specific to their device models.

Workarounds

• Restrict configuration export functionality to trusted administrative users only
• Store exported configuration files in secure, access-controlled locations
• Remove or rotate administrative credentials after any configuration export operation
• Implement network segmentation to limit access to management interfaces
• Consider using strong, complex administrative passwords to increase resistance to offline cracking attacks

# Configuration example for restricting management access
# Limit management interface access to specific trusted IPs
# Consult Moxa documentation for device-specific configuration syntax
# Example network segmentation approach:
# - Place management interfaces on isolated VLAN
# - Implement ACLs to restrict management access to authorized hosts only