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🔥 Overview

A critical authentication bypass vulnerability exists in Android's ADB daemon (adbd) that allows any attacker on the local network to obtain full shell access on a target device without user authorization.

The flaw resides in the adbd_tls_verify_cert() function in daemon/auth.cpp, where EVP_PKEY_cmp() is used as a boolean. When the stored key is an RSA key and the provided TLS client certificate carries a non-RSA key (EC P-256 or Ed25519), EVP_PKEY_cmp() returns -1 (type mismatch), which evaluates as true in C/C++, thus setting authorized = true.

// Vulnerable code pattern in daemon/auth.cpp
if (EVP_PKEY_cmp(peer_key, stored_key)) { // ← BUG: -1 is truthy!
    authorized = true;
}

EVP_PKEY_cmp() Return Value	Meaning	Truthy in C?	Result
1	Keys match	✅	Authorized (correct)
0	Keys differ	❌	Denied (correct)
-1	Type mismatch	✅	Authorized (BUG)

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⚡ Quick Start

Install Dependencies

pip install cryptography

Run the Exploit

# Interactive shell
python adb_tls_auth_bypass.py <TARGET_IP> <PORT>

# Single command execution
python adb_tls_auth_bypass.py 192.168.1.42 37521 --cmd "id"

# Verbose mode (full protocol trace)
python adb_tls_auth_bypass.py 192.168.1.42 37521 -v --cmd "id"

Force a Specific Key Type

python adb_tls_auth_bypass.py 192.168.1.42 5555 --key-type ec
python adb_tls_auth_bypass.py 192.168.1.42 5555 --key-type ed25519

By default, the script automatically tries EC P-256 → Ed25519 → EC/TLS 1.2 until successful.

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🎯 Exploit Flow

Attacker                        Target (adbd)
      │                                    │
│──── TCP Connect ──────────────────►│
│──── CNXN (plaintext) ────────────►│
│◄─── STLS (TLS upgrade request) ──│
│──── STLS Reply ──────────────────►│
      │                                    │
│════ TLS 1.3 Handshake ════════════│
│ (submitted EC P-256 client cert) │
│ EVP_PKEY_cmp(EC, RSA) → -1      │
│ -1 is truthy → authorized=true   │
      │════════════════════════════════════│
      │                                    │
│◄─── CNXN (device info) ──────────│
│──── Open "shell:" ───────────────►│
│◄─── OKAY ────────────────────────│
│◄──► WRTE/OKAY (shell I/O) ──────►│
      │                                    │
【Full shell access】

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📋 Prerequisites

Requirement	Details
Developer Options	Enabled on the target device
Wireless Debugging	Enabled (or ADB over TCP port 5555)
Stored RSA Key	Device must have been paired at least once via USB (/data/misc/adb/adb_keys)
Network Access	Attacker must have access to the adbd TCP port

⚠️ Important: The RSA key must be in the /data/misc/adb/adb_keys file, which is populated through USB debugging pairing (accepting the "Allow USB debugging?" dialog). Wireless debugging pairing (adb pair) stores the key in a different location (adb_known_hosts.pb), so it does not satisfy this requirement.

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🛡️ Affected Versions

• Android 14 (AOSP) — ✅ Confirmed vulnerable
• Android 15 (AOSP) — Likely vulnerable (unpatched builds)
• Vendor-specific builds may vary (e.g., Samsung One UI, Pixel, etc.)

How to Check Patch Level

adb shell getprop ro.build.version.security_patch

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🧪 Test Environment

Confirmed working on the following test environment:

Kernel: 6.1.23-android14-4-00257-g7e35917775b8-ab9964412
Platform: Android 14 (Android Studio Emulator)

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🔧 Improvements Over Original

This fork includes several improvements:

• ✅ Multi-key fallback — Automatically tries EC P-256 → Ed25519 → EC/TLS 1.2
• ✅ Ed25519 support — Alternative key type for wider compatibility
• ✅ TLS 1.2 fallback — Different client certificate flow (sent during handshake vs. after handshake)
• ✅ Enhanced certificates — Proper X.509 extensions (BasicConstraints, KeyUsage)
• ✅ Windows compatible — Uses threaded I/O instead of select() for cross-platform support
• ✅ Increased timeouts — Better reliability on slower networks
• ✅ Verbose diagnostics — Detailed protocol trace with -v flag

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📁 Project Structure

CVE-2026-0073-Android-ADBD-bypass-POC/
├── adb_tls_auth_bypass.py # Main exploit script
└── README.md              # This file

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⚠️ Disclaimer

This tool is intended for authorized security testing and educational purposes only. Unauthorized access to computer systems is illegal. Always obtain proper authorization before testing. The author is not responsible for any misuse of this software.

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📚 References

• CVE-2026-0073 — MITRE
• Android Security Bulletin
• OpenSSL EVP_PKEY_cmp Documentation
• ADB Protocol Reference

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