CVE-2017-20238

Executive Summary

CVE-2017-20238 is an improper authorization vulnerability in Hirschmann Industrial HiVision versions 06.0.00 and 07.0.00 prior to 06.0.06 and 07.0.01. The flaw allows read-only users to gain write access to managed devices by bypassing access control mechanisms. Attackers can exploit alternative interfaces such as the web interface or SNMP browser to modify device configurations despite having restricted permissions. This vulnerability is particularly dangerous in industrial environments where network segmentation and strict access controls are critical.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a proprietary industrial network management software (Hirschmann Industrial HiVision). The supply chain risk is limited to organizations that deploy this specific software in their OT/ICS environments.

CVSS Breakdown & Threat Level

• CVSS Score: 7.1 (High)
• Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: Low (PR:L) – attacker needs read-only access first
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: None (C:N)
• Integrity Impact: High (I:H) – configuration modification
• Availability Impact: Low (A:L) – potential disruption from misconfiguration

Threat Level: High. While the EPSS score is 0.0%, the vulnerability allows privilege escalation from read-only to write access, which can lead to significant operational disruption in industrial networks.

Deep Dive & Mechanics

The vulnerability resides in the authorization logic of Hirschmann Industrial HiVision. The software is designed to enforce role-based access control (RBAC), where read-only users should only be able to view device configurations. However, due to improper authorization checks, the application fails to validate user permissions when requests are made through alternative interfaces (e.g., web UI, SNMP browser). This allows a read-only user to send write requests (e.g., SNMP SET commands, HTTP POST/PUT to configuration endpoints) that are processed without proper permission verification.

The root cause is likely a missing or incomplete authorization check in the backend API or SNMP handler. The application may rely on client-side restrictions or fail to re-validate permissions for each request, assuming that if a user is authenticated, they have the necessary rights.

Vulnerable vs. Patched Code

No specific code diff is publicly available. However, the patch (versions 06.0.06 and 07.0.01) likely introduces server-side authorization checks for all write operations, ensuring that the user's role is verified before processing configuration changes.

Vulnerable behavior:

• User with read-only role can send a write request (e.g., via SNMP SET or HTTP POST) to modify device settings.
• The server processes the request without checking if the user has write permissions.

Patched behavior:

• The server checks the user's role before processing any write request.
• If the user is read-only, the request is rejected with an authorization error.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Access to a Hirschmann Industrial HiVision instance (version 06.0.00 or 07.0.00).
• A valid read-only user account.

Exploitation Steps:

1. Identify Alternative Interfaces: Scan the HiVision server for open ports (e.g., 80/443 for web, 161 for SNMP).
2. Authenticate as Read-Only User: Log in via the web interface or SNMP with the read-only credentials.
3. Bypass Authorization:
   • Web Interface: Use a tool like Burp Suite to intercept and modify requests. For example, change a GET request to a POST request targeting a configuration endpoint (e.g., /config/device/set).
   • SNMP Browser: Use an SNMP tool (e.g., MIB Browser) to send SNMP SET requests to modify device parameters (e.g., community string, IP address).
4. Confirm Write Access: Verify that the configuration change was applied (e.g., device settings updated).

Example SNMP SET command (using snmpset):

snmpset -v2c -c public_read 192.168.1.100 1.3.6.1.4.1.248.1.2.1.1.1.0 s "new_value"

Note: The actual OID and value will depend on the target device.

Blue Team

Detection:

• Monitor for SNMP SET requests from users who should only have read access.
• Log all configuration changes and correlate them with user roles.
• Alert on write operations performed by read-only users.

Prevention:

• Apply the vendor patch immediately.
• Implement network segmentation to limit access to HiVision servers.
• Use strict firewall rules to allow only necessary protocols (e.g., SNMP read-only from specific IPs).
• Enable detailed logging and audit trails for all configuration changes.

Indicators of Compromise (IOCs)

• Network IOCs:
  • SNMP SET requests from unexpected source IPs or users.
  • HTTP POST requests to configuration endpoints from read-only user sessions.
• System IOCs:
  • Unauthorized changes to device configurations (e.g., modified SNMP community strings, IP addresses).
  • Log entries showing write operations by users with read-only roles.
• File IOCs:
  • HiVision log files containing authorization failures or unexpected write operations.

Detection Engineering

YARA Rule

rule CVE_2017_20238_Hirschmann_HiVision_Authorization_Bypass {
    meta:
        description = "Detects attempts to exploit CVE-2017-20238 in Hirschmann Industrial HiVision logs"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2017-20238"
    strings:
        $s1 = "Authorization failed" nocase
        $s2 = "write operation" nocase
        $s3 = "read-only" nocase
        $s4 = "configuration change" nocase
    condition:
        any of ($s*) and #s1 > 0
}

Sigma Rule

title: Hirschmann HiVision Authorization Bypass (CVE-2017-20238)
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects write operations performed by read-only users in Hirschmann HiVision logs
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2017-20238
logsource:
    product: hirschmann
    service: hivision
detection:
    selection:
        EventID: 4624  # Example: Windows Security Log for user authentication
        UserRole: "read-only"
        Operation: "write"
    condition: selection
falsepositives:
    - Legitimate administrative actions after role change
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET 80 (msg:"CVE-2017-20238 Hirschmann HiVision Authorization Bypass - HTTP POST to config endpoint"; flow:to_server,established; content:"POST"; http_method; content:"/config/"; http_uri; content:"set"; http_uri; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Patch: Upgrade Hirschmann Industrial HiVision to version 06.0.06 or 07.0.01.
2. Workaround: If patching is not possible, restrict access to the HiVision web interface and SNMP service to trusted IPs only.
3. Review User Roles: Audit all user accounts and ensure that read-only users do not have unnecessary permissions.

Long-Term Measures:

• Implement network segmentation for OT/ICS environments.
• Use multi-factor authentication for all administrative access.
• Regularly review and update access control policies.
• Monitor logs for unauthorized configuration changes.

Valters IT Signature This report was generated by Valters IT DevSecOps AI Assistant. For questions, contact Secure Channels (Signal / Portal).

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