CVE-2018-25236: Hirschmann HiOS Authentication Bypass Flaw

CVE-2018-25236 Overview

CVE-2018-25236 is a critical authentication bypass vulnerability affecting Hirschmann HiOS and HiSecOS industrial networking products. The vulnerability exists in the HTTP(S) management module and allows unauthenticated remote attackers to gain administrative access by crafting specially formed HTTP requests. Attackers can exploit improper authentication handling to obtain the authentication status and privileges of a previously authenticated user without providing valid credentials.

Critical Impact

Unauthenticated remote attackers can gain full administrative access to industrial networking equipment, potentially compromising critical infrastructure and operational technology (OT) environments.

Affected Products

• Hirschmann RSP, RSPE, RSPS, RSPL series
• Hirschmann MSP, EES, EESX, GRS, OS series
• Hirschmann RED, EAGLE series

Discovery Timeline

• 2026-04-03 - CVE-2018-25236 published to NVD
• 2026-04-07 - Last updated in NVD database

Technical Details for CVE-2018-25236

Vulnerability Analysis

This authentication bypass vulnerability (CWE-287) affects the HTTP(S) management module in Hirschmann HiOS and HiSecOS products. The flaw stems from improper authentication handling that allows attackers to inherit the authentication status and privileges of previously authenticated users without presenting valid credentials. This is particularly dangerous in industrial control system (ICS) environments where these devices are commonly deployed to manage critical network infrastructure.

The vulnerability enables attackers to bypass the authentication mechanism entirely through specially crafted HTTP requests, granting them the same level of access as legitimate administrators. This could lead to complete device compromise, configuration manipulation, and potential disruption of industrial operations.

Root Cause

The root cause is improper authentication validation (CWE-287) in the HTTP(S) management module. The web server component fails to properly validate authentication state for incoming requests, allowing attackers to craft requests that the system interprets as already authenticated. This session management flaw enables credential-less access by exploiting the authentication state inheritance mechanism.

Attack Vector

The attack vector is network-based, requiring no user interaction and no prior privileges. An attacker with network access to the management interface can send specially crafted HTTP requests to the device's web management module. These requests manipulate the authentication handling logic to assume the identity and privileges of a previously authenticated session, effectively bypassing all authentication controls.

The exploitation process involves:

1. Identifying a vulnerable Hirschmann HiOS or HiSecOS device with an exposed HTTP(S) management interface
2. Crafting malformed HTTP requests that exploit the authentication state inheritance flaw
3. Sending the crafted requests to gain administrative access without credentials
4. Executing privileged operations on the device with full administrative control

Detection Methods for CVE-2018-25236

Indicators of Compromise

• Unexpected administrative configuration changes on Hirschmann devices without corresponding authenticated sessions
• Anomalous HTTP requests to the management interface with unusual or malformed headers
• Access logs showing administrative operations without valid authentication entries
• Multiple successful administrative sessions originating from unknown or suspicious IP addresses

Detection Strategies

• Monitor HTTP(S) traffic to Hirschmann device management interfaces for malformed authentication requests
• Implement network segmentation monitoring to detect unauthorized access attempts to OT/ICS network segments
• Deploy intrusion detection systems (IDS) with signatures for authentication bypass patterns targeting industrial devices
• Analyze access logs for administrative operations that lack corresponding successful authentication events

Monitoring Recommendations

• Enable verbose logging on all Hirschmann HiOS and HiSecOS devices and forward logs to a centralized SIEM
• Implement network traffic analysis for anomalous HTTP patterns targeting device management ports (typically 80/443)
• Configure alerts for any administrative access from IP addresses outside approved management networks
• Regularly audit device configurations for unauthorized changes that may indicate compromise

How to Mitigate CVE-2018-25236

Immediate Actions Required

• Isolate affected Hirschmann devices from untrusted network segments immediately
• Disable HTTP(S) management interfaces if not operationally required, or restrict access via firewall rules to trusted management hosts only
• Apply vendor-provided firmware updates as documented in the Belden Security Bulletin
• Implement network segmentation to ensure management interfaces are only accessible from dedicated management VLANs

Patch Information

Belden (Hirschmann's parent company) has released security updates to address this vulnerability. Administrators should consult the Belden Security Bulletin for specific firmware versions and upgrade instructions. The VulnCheck Security Advisory provides additional technical details.

Workarounds

• Restrict management interface access to specific trusted IP addresses using device ACLs or external firewalls
• Implement jump hosts or bastion servers for administrative access to industrial networking equipment
• Disable the web management interface and use alternative management methods such as CLI via serial console or SSH if available
• Deploy network monitoring to detect and alert on any access attempts to management interfaces from unauthorized sources

# Example firewall configuration to restrict management access
# Restrict HTTP/HTTPS management to trusted management network only
iptables -A INPUT -p tcp --dport 80 -s 192.168.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 192.168.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP