Programmatic Vulnerability Remediations on Linux

Automate vulnerability remediation with scripting (Bash)

Vulnerability Management Lab (Azure + Tenable)

This lab demonstrates how to provision a Linux VM in Azure, perform vulnerability scanning using Tenable with DISA STIG compliance, introduce vulnerabilities intentionally, and apply automated remediation using bash scripts.

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Table of Contents

• 🚀 Step 1: Provision a Linux VM in Azure
• 🔧 Step 2: Configure Network & Access
• 📱 Step 3: Test Connectivity
• 🔍 Step 4: Initial Vulnerability Scan with Tenable
• 🧪 Step 5: Introduce Vulnerabilities
  • 5.1 Install Insecure Telnet Service
  • 5.2 Enable Root Login over SSH
  • 5.3 Set Insecure Root Password
• 🔄 Step 6: Second Vulnerability Scan
• 🧰 Step 7: Run Remediation Scripts
  • 7.1 Remediate Default Root Password
  • 7.2 Remediate OpenSSL 305
  • 7.3 Remove Telnet Service
• 🔄 Step 8: Final Scan & Validation
• 🧹 Step 9: Clean Up
• 📊 Summary
• 🔗 References

🚀 Step 1: Provision a Linux VM in Azure

• Select a secure Linux distribution (e.g., Ubuntu 22.04 LTS).
• Avoid using default credentials like labuser/Cyberlab123!.

• Configure the VM with:

  • Password authentication (for lab only)
  • Public IP enabled
  • NSG rules allowing SSH (port 22)
  • OS Disk type: Standard HDD

  

⚠️ Do not leave weak passwords or root access open — past labs have been breached due to exposed cloud VMs.

🔒 Authentication

• Default method is SSH key pair.
• For lab purposes, set a strong password, but remember to delete the VM after testing.

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🔧 Step 2: Configure Network & Access

• In Azure, make sure your Network Security Group (NSG) includes:

  • Inbound Rule: SSH (TCP/22)
  • Inbound Rule: ICMP (Ping)
  • Inbound Rule: Telnet (TCP/23) — temporarily for testing

⚠️ Only open Telnet for lab use and close it immediately after validation.

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📱 Step 3: Test Connectivity

After VM is deployed and running:

ping <vm-public-ip>
ssh <username>@<vm-public-ip>

Make sure:

• VM is reachable

• SSH login is successful

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🔍 Step 4: Initial Vulnerability Scan with Tenable

• Log in to cloud.tenable.com
• Create a new authenticated scan (Scan1)
• Use the Linux DISA STIG compliance template

• Scanner Type:

  • Use Internal Engine

• Set scan target to the internal IP of the VM

• Provide valid SSH credentials

• Launch the scan

• Export results (PDF or CSV)

Scan 1 Report - Baseline

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🧪 Step 5: Introduce Vulnerabilities

Login to your VM using SSH, then:

5.1 Install Insecure Telnet Service

sudo apt update
sudo apt install telnetd -y
sudo systemctl enable inetd.service
sudo systemctl start inetd.service
sudo systemctl status inetd.service

⚠️ Telnet is insecure and should be removed after testing.

5.2 Enable Root Login over SSH

sudo grep -q '^PermitRootLogin' /etc/ssh/sshd_config && \
  sudo sed -i 's/^PermitRootLogin.*/PermitRootLogin yes/' /etc/ssh/sshd_config || \
  echo 'PermitRootLogin yes' | sudo tee -a /etc/ssh/sshd_config

sudo systemctl restart sshd

5.3 Set Insecure Root Password

sudo passwd root
# Enter password: root

⚠️ After enabling root, destroy or disable the VM immediately post-testing. Previous labs were compromised via open root logins.

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🔄 Step 6: Second Vulnerability Scan

• Launch a second authenticated scan after introducing vulnerabilities

• Validate findings:

  • Unencrypted Telnet service
  • Insecure root credentials

• Export the results

Scan 2 - Vulnerbility Detection

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🧰 Step 7: Run Remediation Scripts

Use provided bash scripts to remediate each finding.

7.1 Remediate Default Root Password

🔗 GitHub Script – Root Password

7.2 Remediate OpenSSL 3.0.5

🔗 GitHub Script – OpenSSL

7.3 Remove Telnet Service

🔗 GitHub Script – Telnet

🛠 How to run the scripts:

chmod +x scriptname.sh
sudo ./scriptname.sh

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🔄 Step 8: Final Scan & Validation

• Reboot the VM:

sudo reboot

• Run a final authenticated scan in Tenable

• Confirm:

  • Telnet is removed
  • Root password is changed
  • OpenSSL is updated (if applicable)

• Export final scan results

Scan 3 Report - Remediated

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🧹 Step 9: Clean Up

Delete the VM to prevent exposure or costs:

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📊 Summary

Stage	Task
✅	Linux VM provisioned in Azure
✅	NSG rules configured
✅	Tenable baseline scan (Scan 1)
✅	Vulnerabilities introduced
✅	Second scan performed (Scan 2)
✅	Remediation scripts executed
✅	Final scan (Scan 3) and validation
✅	VM deleted

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🔗 References

• Tenable Documentation
• DISA STIG Benchmarks
• Azure VM Documentation
• Remediation Scripts by Josh Madakor

🔐 This lab simulates an enterprise workflow of provision → assess → harden → validate.