CVE-2026-24061 GNU Inetutils Telnetd Authentication Bypass Vulnerability Detection Tool

📋 Project Overview

This is an advanced detection tool for the GNU Inetutils Telnetd authentication bypass vulnerability (CVE-2026-24061). This vulnerability has a CVSS score of 9.8, allowing attackers to obtain root privileges without authentication through environment variable injection.

🚨 Vulnerability Information

• CVE ID: CVE-2026-24061
• CVSS Score: 9.8 (Critical)
• Affected Versions: GNU Inetutils 1.9.3 - 2.7
• Vulnerability Type: Authentication Bypass
• Technical Principle: Environment variable injection based on RFC 1572 standard

📦 Features

• ✅ Multi-threaded Batch Detection - Supports concurrent scanning of multiple targets
• ✅ Intelligent Vulnerability Identification - Multiple detection methods based on uid=0/gid=0 characteristics
• ✅ Detailed Output Mode - Supports colored terminal output and detailed logging
• ✅ Result Export - Can save vulnerability results to a file
• ✅ Protocol Standard Implementation - Based on RFC 1572 Telnet protocol standard
• ✅ Cross-platform Support - Supports Windows/Linux/macOS

🔧 System Requirements

• Python 3.6+
• Network access permissions
• Target system must be running GNU Inetutils Telnetd service

Optional Dependencies

# Windows system color support
pip install colorama

🚀 Quick Start

1. Single Target Detection

python3 CVE-2026-24061.py 192.168.1.1

2. Batch Detection

# Create target file
echo "192.168.1.1" > targets.txt
echo "192.168.1.2" >> targets.txt
echo "192.168.1.3" >> targets.txt

# Execute batch detection
python3 CVE-2026-24061.py -f targets.txt

3. Advanced Parameter Configuration

# Specify port and thread count
python3 CVE-2026-24061.py -f targets.txt -p 23 -t 50

# Verbose mode and save results
python3 CVE-2026-24061.py -f targets.txt -o results.txt -v

# Custom timeout
python3 CVE-2026-24061.py -f targets.txt -T 10

📊 Detection Result Description

Detection Status Indicators

Status	Indicator	Color	Description
Confirmed Vulnerability	✓	🔴 Red	Both uid=0 and gid=0 detected
Highly Suspicious	⚠	🟡 Yellow	uid=0 and root user detected
Needs Confirmation	?	🔵 Cyan	Only uid=0 detected, manual verification required
Safe	✗	🟢 Green	No vulnerability characteristics detected
Connection Failed	✗	⚪ Gray	Network connection issue

Output Example

[✓ Confirmed Vulnerability] [14:30:25] 192.168.1.1:23 └─ Confirmed Vulnerability | uid=0/gid=0 | Banner: Ubuntu 20.04

[⚠ Highly Suspicious] [14:30:26] 192.168.1.2:23 └─ Highly Suspicious | uid=0 + root | Banner: Debian 12

[? Needs Confirmation] [14:30:27] 192.168.1.3:23 └─ uid=0 detected but missing other confirmation conditions

⚙️ Parameter Details

Basic Parameters

Parameter	Abbreviation	Default Value	Description
--file	-f	-	Target file path
--port	-p	23	Target port
--threads	-t	50	Number of concurrent threads
--timeout	-T	8	Timeout per target (seconds)
--output	-o	-	Result output file
--verbose	-v	False	Verbose output mode
--user	-u	root	Authentication username

Target File Format

The target file supports the following formats: 192.168.1.1 192.168.1.2:2323 # Specify port 192.168.1.0/24 # CIDR format 10.0.0.1-10.0.0.10 # IP range

🔬 Technical Principle

Vulnerability Mechanism

This vulnerability exploits the improper handling of environment variables in GNU Inetutils Telnetd:

1. Protocol Negotiation: Based on RFC 1572 Telnet NEW-ENVIRON protocol
2. Environment Variable Injection: Passing the "-f root" parameter through the USER environment variable
3. Authentication Bypass: The login program executes the /bin/login -f root command
4. Privilege Escalation: The system skips password verification and directly grants root privileges

Detection Logic

# Multiple detection conditions
uid_0_detected = "uid=0" in response_text
gid_0_detected = "gid=0" in response_text
root_detected = "root" in response_text

# Vulnerability confirmation logic
if uid_0_detected and gid_0_detected:
    return "Confirmed Vulnerability"
elif uid_0_detected and root_detected:
    return "Highly Suspicious"
elif uid_0_detected:
    return "Needs Confirmation"

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