Back to Vulnerability Database

Cleartext Transmission of Sensitive Information

Description

Cleartext Transmission of Sensitive Information occurs when software transmits sensitive or security-critical data in cleartext over a communication channel that can be intercepted by unauthorized actors. This includes sending passwords, session tokens, personal information, financial data, or API keys over unencrypted HTTP connections, unencrypted protocols (FTP, Telnet, SMTP without TLS), or poorly configured network connections. When data travels without encryption, anyone positioned to observe network traffic—through network sniffing, man-in-the-middle attacks, or compromised network infrastructure—can capture and read the transmitted information.

Risk

Cleartext transmission exposes all data in transit to interception. Session sidejacking attacks capture unencrypted session tokens, enabling attackers to hijack authenticated sessions. IBM DevOps Deploy (CVE-2025-13489) transmitted sensitive data in cleartext allowing man-in-the-middle attacks. Schneider Electric products (CVE-2025-1060) exposed data through unencrypted network communications. Passwords transmitted in cleartext enable immediate account takeover. Financial data interception facilitates fraud. On shared networks (WiFi, corporate LANs), attackers can passively capture all unencrypted traffic. This vulnerability enables both passive eavesdropping and active man-in-the-middle attacks.

Solution

Always transmit sensitive data over encrypted channels. Use HTTPS with TLS 1.2+ for web traffic. Implement HSTS to prevent protocol downgrade attacks. Configure email servers with STARTTLS or implicit TLS. Replace legacy protocols (FTP, Telnet) with secure alternatives (SFTP, SSH). Use TLS for database connections. Encrypt API communications. Implement certificate pinning for mobile applications. Configure secure WebSocket connections (WSS). Audit network communications for cleartext transmission. Use VPNs for internal network traffic when appropriate.

Common Consequences

ImpactDetails
ConfidentialityScope: Data Interception

All transmitted sensitive data can be captured and read by network observers.
AuthenticationScope: Session Hijacking

Intercepted credentials and session tokens enable account takeover and impersonation.
IntegrityScope: Data Manipulation

Man-in-the-middle attackers can modify data in transit when no encryption provides integrity protection.

Example Code + Solution Code

Vulnerable Code

# VULNERABLE: HTTP instead of HTTPS
import requests

def login(username, password):
    # Credentials sent in cleartext over HTTP!
    response = requests.post('http://api.example.com/login',
                             data={'username': username, 'password': password})
    return response.json()

# VULNERABLE: Unencrypted database connection
import psycopg2

conn = psycopg2.connect(
    host='database.example.com',
    database='mydb',
    user='admin',
    password='secret'  # No SSL - credentials sent in cleartext!
)

// VULNERABLE: HTTP URL for sensitive operations
import java.net.HttpURLConnection;
import java.net.URL;

public class PaymentService {
    public void processPayment(String cardNumber, String cvv) throws Exception {
        // Payment data sent over unencrypted HTTP!
        URL url = new URL("http://payment.example.com/process");
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestMethod("POST");

        String data = "card=" + cardNumber + "&cvv=" + cvv;
        conn.getOutputStream().write(data.getBytes());
    }
}

// VULNERABLE: WebSocket without encryption
const socket = new WebSocket('ws://chat.example.com/messages');

socket.onopen = function() {
    // Messages sent in cleartext!
    socket.send(JSON.stringify({
        type: 'auth',
        token: authToken
    }));
};

// VULNERABLE: Form without HTTPS
<form action="http://example.com/login" method="POST">
    <input type="password" name="password">
    <button type="submit">Login</button>
</form>

Fixed Code

# SAFE: HTTPS with certificate verification
import requests
import ssl
import psycopg2

def login_safe(username, password):
    # Credentials encrypted with TLS
    response = requests.post('https://api.example.com/login',
                             data={'username': username, 'password': password},
                             verify=True)  # Verify certificate (default)
    return response.json()

# SAFE: Encrypted database connection with SSL
conn = psycopg2.connect(
    host='database.example.com',
    database='mydb',
    user='admin',
    password='secret',
    sslmode='verify-full',  # Require SSL and verify certificate
    sslrootcert='/path/to/ca-certificate.crt'
)

# SAFE: SMTP with TLS
import smtplib
from email.message import EmailMessage

def send_email_safe(to, subject, body):
    msg = EmailMessage()
    msg['Subject'] = subject
    msg['To'] = to
    msg.set_content(body)

    # Use TLS encryption
    with smtplib.SMTP_SSL('smtp.example.com', 465) as server:
        server.login('user', 'password')  # Encrypted connection
        server.send_message(msg)

// SAFE: HTTPS with proper certificate validation
import javax.net.ssl.HttpsURLConnection;
import java.net.URL;

public class PaymentService {
    public void processPayment(String cardNumber, String cvv) throws Exception {
        // Payment data encrypted with TLS
        URL url = new URL("https://payment.example.com/process");
        HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
        conn.setRequestMethod("POST");

        // Additional security headers
        conn.setRequestProperty("Strict-Transport-Security", "max-age=31536000");

        String data = "card=" + cardNumber + "&cvv=" + cvv;
        conn.getOutputStream().write(data.getBytes());
    }
}

// SAFE: Enforce HTTPS in Spring Boot
@Configuration
public class SecurityConfig extends WebSecurityConfigurerAdapter {
    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http.requiresChannel()
            .anyRequest()
            .requiresSecure();  // Force HTTPS

        http.headers()
            .httpStrictTransportSecurity()
            .includeSubDomains(true)
            .maxAgeInSeconds(31536000);
    }
}

// SAFE: Secure WebSocket (WSS)
const socket = new WebSocket('wss://chat.example.com/messages');

socket.onopen = function() {
    // Messages encrypted with TLS
    socket.send(JSON.stringify({
        type: 'auth',
        token: authToken
    }));
};

// SAFE: Force HTTPS in Express.js
const express = require('express');
const helmet = require('helmet');

const app = express();

// Enable HSTS
app.use(helmet.hsts({
    maxAge: 31536000,
    includeSubDomains: true,
    preload: true
}));

// Redirect HTTP to HTTPS
app.use((req, res, next) => {
    if (req.header('x-forwarded-proto') !== 'https') {
        res.redirect(`https://${req.header('host')}${req.url}`);
    } else {
        next();
    }
});

Exploited in the Wild

IBM DevOps Deploy (IBM, 2025)

CVE-2025-13489 in IBM DevOps Deploy allowed attackers to intercept sensitive data using man-in-the-middle techniques due to cleartext transmission, rated CVSS 5.9.

Schneider Electric Industrial Systems (Schneider Electric, 2025)

CVE-2025-1060 in Schneider Electric products exposed data when network traffic was sniffed due to cleartext transmission of sensitive information.

Firesheep WiFi Session Hijacking (Multiple, 2010-Present)

The Firesheep browser extension demonstrated mass session hijacking on open WiFi networks by capturing unencrypted session cookies, leading to widespread adoption of HTTPS.

Tools to test/exploit

  • Wireshark — network protocol analyzer to capture cleartext traffic.

  • mitmproxy — intercept and inspect HTTP/HTTPS traffic.

  • Ettercap — man-in-the-middle attack framework.

CVE Examples

References

  1. MITRE. "CWE-319: Cleartext Transmission of Sensitive Information." https://cwe.mitre.org/data/definitions/319.html

  2. OWASP. "Transport Layer Protection Cheat Sheet." https://cheatsheetseries.owasp.org/cheatsheets/Transport_Layer_Protection_Cheat_Sheet.html