CVE-2018-25237: Hirschmann HiSecOS RCE Vulnerability

CVE-2018-25237 Overview

CVE-2018-25237 is a critical buffer overflow vulnerability affecting Hirschmann HiSecOS devices running firmware versions prior to 05.3.03. The vulnerability exists in the HTTPS login interface when RADIUS authentication is enabled, allowing remote attackers to crash the device or execute arbitrary code by submitting a password longer than 128 characters.

Critical Impact

Remote attackers can exploit this vulnerability without authentication to achieve denial of service or remote code execution on affected industrial networking devices.

Affected Products

• Hirschmann HiSecOS devices with firmware versions prior to 05.3.03
• Devices configured with RADIUS authentication enabled
• Industrial network security appliances in the HiSecOS product line

Discovery Timeline

• 2026-04-03 - CVE CVE-2018-25237 published to NVD
• 2026-04-07 - Last updated in NVD database

Technical Details for CVE-2018-25237

Vulnerability Analysis

This vulnerability stems from improper bounds checking in the password handling routine of the HTTPS login interface. When RADIUS authentication is enabled, the affected devices allocate a fixed-size buffer of 128 characters for storing user-supplied passwords. The code fails to validate the length of incoming password data before copying it into this buffer, creating a classic buffer overflow condition.

The vulnerability is classified as CWE-120 (Buffer Copy without Checking Size of Input), which represents one of the most dangerous memory corruption vulnerability classes. An attacker can exploit this flaw remotely over the network without requiring any authentication or user interaction, making it particularly severe for internet-exposed devices.

Root Cause

The root cause is the absence of proper input validation on user-supplied password data during the HTTPS authentication process. The firmware's login handler accepts password input directly from the network and copies it into a fixed-size stack or heap buffer without first verifying that the input length does not exceed the buffer's capacity. This allows attackers to write beyond the allocated memory region.

Attack Vector

The attack can be executed remotely over the network by any unauthenticated attacker who can reach the device's HTTPS management interface. The exploitation process involves:

1. Establishing an HTTPS connection to the target device's management interface
2. Initiating a login attempt with RADIUS authentication
3. Submitting a crafted password exceeding 128 characters
4. The overflow corrupts adjacent memory, potentially overwriting return addresses or function pointers
5. Depending on the payload, this results in device crash (denial of service) or arbitrary code execution

The attack requires no special privileges or user interaction. For detailed technical information, refer to the VulnCheck Advisory on Buffer Overflow and the Belden Security Bulletin.

Detection Methods for CVE-2018-25237

Indicators of Compromise

• Unexpected device reboots or crashes, particularly on HiSecOS appliances with RADIUS enabled
• Anomalous HTTPS POST requests to the login endpoint containing unusually long password parameters
• Network traffic analysis showing oversized credential submissions (passwords exceeding 128 bytes)
• Device logs showing authentication failures followed by system instability

Detection Strategies

• Monitor HTTPS traffic to HiSecOS management interfaces for POST requests with password fields exceeding 128 characters
• Implement network intrusion detection rules to flag oversized authentication payloads targeting industrial device management ports
• Deploy application-layer firewalls capable of inspecting and limiting input field lengths on login forms
• Configure SIEM rules to correlate authentication attempts with subsequent device availability issues

Monitoring Recommendations

• Enable comprehensive logging on HiSecOS devices and forward logs to a centralized security monitoring platform
• Monitor device health metrics for unexpected restarts or resource exhaustion patterns
• Implement network segmentation to limit exposure of industrial device management interfaces
• Conduct regular firmware version audits to identify devices running vulnerable versions prior to 05.3.03

How to Mitigate CVE-2018-25237

Immediate Actions Required

• Upgrade all affected Hirschmann HiSecOS devices to firmware version 05.3.03 or later immediately
• Restrict network access to the HTTPS management interface using firewall rules and network segmentation
• Consider temporarily disabling RADIUS authentication if the upgrade cannot be applied immediately
• Isolate vulnerable devices from untrusted network segments until patching is complete

Patch Information

Belden/Hirschmann has released firmware version 05.3.03 which addresses this vulnerability. Organizations should obtain the patched firmware through official Belden support channels. The Belden Security Bulletin provides detailed information about the security update.

Workarounds

• Disable RADIUS authentication and use local authentication until the patch can be applied
• Implement strict network access controls to limit which hosts can connect to the management interface
• Deploy a web application firewall (WAF) or reverse proxy in front of the management interface to enforce input length limits
• Use VPN-only access for device management to reduce the attack surface

# Network segmentation example using firewall rules
# Restrict HTTPS management access to trusted management network only
iptables -A INPUT -p tcp --dport 443 -s 10.0.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP