CVE-2024-1039: Gesslergmbh Web-master Auth Bypass Flaw

CVE-2024-1039 Overview

CVE-2024-1039 is a hardcoded credentials vulnerability affecting the Gessler GmbH WEB-MASTER device. The vulnerability exists due to a restoration account that uses weak hard-coded credentials within the device firmware. If successfully exploited, an attacker could gain unauthorized control over the web management interface of the affected industrial control system device.

Critical Impact

Successful exploitation allows an attacker to gain complete administrative control over the WEB-MASTER device's web management interface, potentially compromising critical industrial control system infrastructure.

Affected Products

• Gessler GmbH WEB-MASTER Firmware version 7.9
• Gessler GmbH WEB-MASTER hardware device
• Industrial control systems utilizing WEB-MASTER for web-based management

Discovery Timeline

• 2024-02-01 - CVE-2024-1039 published to NVD
• 2025-08-07 - Last updated in NVD database

Technical Details for CVE-2024-1039

Vulnerability Analysis

This vulnerability is classified under CWE-798 (Use of Hard-coded Credentials) and CWE-287 (Improper Authentication). The Gessler GmbH WEB-MASTER device contains a restoration account with weak, hard-coded credentials embedded directly in the firmware. This design flaw allows any attacker with network access to the device to authenticate using these known credentials, bypassing normal authentication mechanisms.

The vulnerability is particularly concerning in industrial control system (ICS) environments where the WEB-MASTER device may be deployed to manage critical infrastructure. Hard-coded credentials represent a fundamental security flaw as they cannot be changed by administrators and remain constant across all deployed devices of the same firmware version.

Root Cause

The root cause of this vulnerability is the implementation of a restoration account with static, hard-coded credentials within the WEB-MASTER firmware. This practice violates secure development principles as it creates a universal backdoor that cannot be mitigated through normal password management practices. The weak nature of these credentials further compounds the risk, as they may be easily guessed or discovered through firmware analysis.

Attack Vector

The attack vector for CVE-2024-1039 is network-based, requiring no prior authentication or user interaction. An attacker with network access to the WEB-MASTER device can attempt authentication using the hard-coded credentials. The attack complexity is low, as exploitation simply requires knowledge of the default credentials and network connectivity to the target device's web management interface.

Attackers may discover these credentials through:

• Reverse engineering the device firmware
• Analyzing vendor documentation or support forums
• Discovering credentials published in security advisories or vulnerability databases
• Using default credential lists commonly employed in penetration testing

Once authenticated, the attacker gains full control over the device's web management interface, enabling configuration changes, monitoring capabilities, and potential pivoting to other connected systems.

Detection Methods for CVE-2024-1039

Indicators of Compromise

• Unexpected or unauthorized login events to the WEB-MASTER web management interface
• Authentication attempts using the restoration account from external or unknown IP addresses
• Configuration changes made outside of normal maintenance windows
• Multiple failed authentication attempts followed by successful login using the restoration account

Detection Strategies

• Implement network monitoring to detect authentication attempts to WEB-MASTER devices from unauthorized sources
• Deploy intrusion detection systems (IDS) with rules to identify access patterns consistent with default credential exploitation
• Establish baseline normal access patterns and alert on anomalous authentication activity
• Monitor for firmware extraction or reverse engineering attempts on network traffic

Monitoring Recommendations

• Enable detailed logging on all WEB-MASTER devices and centralize logs for analysis
• Implement real-time alerting for any successful authentication using the restoration account
• Conduct regular audits of device access logs to identify unauthorized access attempts
• Monitor network segments containing ICS devices for reconnaissance activity

How to Mitigate CVE-2024-1039

Immediate Actions Required

• Consult the CISA ICS Advisory ICSA-24-032-01 for vendor-specific guidance
• Implement network segmentation to isolate WEB-MASTER devices from untrusted networks
• Deploy firewall rules to restrict access to the web management interface to authorized IP addresses only
• Place WEB-MASTER devices behind VPN or other secure remote access solutions

Patch Information

Organizations should refer to the CISA ICS Advisory ICSA-24-032-01 for the latest information on available patches or firmware updates from Gessler GmbH. Contact the vendor directly to inquire about firmware versions that address this hard-coded credential vulnerability.

Workarounds

• Implement strict network access controls to limit connectivity to the WEB-MASTER web interface to trusted management stations only
• Deploy a web application firewall (WAF) or reverse proxy in front of the device to add an additional authentication layer
• Use network monitoring tools to detect and block unauthorized access attempts to the device
• Consider physical isolation of affected devices until a patch is available
• Implement multi-factor authentication at the network perimeter for access to ICS network segments

# Network segmentation example using iptables
# Restrict access to WEB-MASTER management interface (example IP: 192.168.1.100)
iptables -A INPUT -p tcp -d 192.168.1.100 --dport 80 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp -d 192.168.1.100 --dport 443 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -p tcp -d 192.168.1.100 --dport 80 -j DROP
iptables -A INPUT -p tcp -d 192.168.1.100 --dport 443 -j DROP