🚨 CVE-2026-4480 - Critical Remote Code Execution in Samba Printing Subsystem

Remote Code Execution (RCE)
Samba Print Command Injection Vulnerability

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"A single print job name should never become a shell command."

📖 Overview

CVE-2026-4480 is a critical command injection vulnerability affecting Samba's printing subsystem.

Under specific configurations, Samba may pass a user-controlled print job name (%J) into a shell command without sufficient sanitization, potentially allowing an attacker to execute arbitrary commands on the affected server.

🎯 Vulnerability Details

🔍 Root Cause

The issue occurs when Samba is configured with a custom printing command similar to:

print command = lp -t %J %s

The %J parameter expands to the print job name supplied by a client.

If this value reaches a shell interpreter without proper escaping or validation, special characters may alter command execution behavior.

⚡ Potential Impact

Successful exploitation may allow an attacker to:

• 💀 Execute arbitrary operating system commands
• 📂 Access sensitive files
• 🗑️ Delete or modify data
• 🦠 Deploy malware or backdoors
• 🔑 Escalate privileges depending on service configuration
• 🌐 Fully compromise the server

📦 Affected Versions

✅ Fixed Versions

Samba 4.22.10
Samba 4.23.8
Samba 4.24.3
and newer releases

🛡️ Mitigation

Immediate Actions

+ Upgrade Samba immediately
+ Review all print command configurations
+ Restrict access to shared printers
+ Disable unnecessary printing services
+ Monitor logs for suspicious print job names

🔎 Detection

Check for custom print commands:

grep -Ri "print command" /etc/samba/

Review results for usage of:

%J

inside shell-executed commands.

📊 Attack Surface

Attacker
    │
    ▼
Submit Print Job
    │
    ▼
User-Controlled Job Name (%J)
    │
    ▼
Shell Command Execution
    │
    ▼
Remote Code Execution

🧠 Technical Classification

📚 References

• Samba Security Advisory
• NIST National Vulnerability Database
• CWE-78: OS Command Injection

⚠️ Disclaimer

This repository is provided for:

• Security awareness
• Vulnerability research
• Defensive validation
• Patch verification

No exploit code or offensive tooling is included.