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How the mentioned CVE works:
The vulnerability exists within the Eclipse Paho MQTT client library’s default configuration for TLS connections. During the TLS handshake process, the client fails to properly validate the server’s X.509 certificate against the intended hostname. This lack of hostname verification means the client will accept any valid certificate from a trusted Certificate Authority, regardless of whether the certificate’s Common Name or Subject Alternative Name fields match the server’s hostname. An attacker positioned as a Man-in-the-Middle can exploit this by presenting a certificate for a different domain they control, provided it is signed by a CA the client trusts. This allows the interception, decryption, and potential modification of all MQTT communication between the client and the broker, compromising the confidentiality and integrity of the message payloads without the client’s knowledge.
Platform: Eclipse Paho MQTT
Version: (Versions prior to patch)
Vulnerability: TLS Hostname Verification
Severity: High
date: 2025-11-06
Prediction: Patch expected 2025-11-20
What Undercode Say:
Checking for the presence of the vulnerable library in a project find . -name ".jar" | grep -i paho
// Vulnerable code example: Creating a client without hostname verification
MqttClient client = new MqttClient("ssl://broker.example.com:8883", MqttClient.generateClientId());
MqttConnectOptions options = new MqttConnectOptions();
// Hostname verification is not enabled by default
client.connect(options);
// Secure code example: Enforcing hostname verification
MqttConnectOptions secureOptions = new MqttConnectOptions();
Properties sslProps = new Properties();
sslProps.setProperty("com.ibm.ssl.protocol", "TLS");
sslProps.setProperty("com.ibm.ssl.hostnameVerification", "true"); // Critical setting
secureOptions.setSSLProperties(sslProps);
client.connect(secureOptions);
How Exploit:
Intercept TLS connection.
Present valid CA-signed certificate.
Bypass hostname validation.
Decrypt/modify MQTT traffic.
Protection from this CVE
Update Paho library.
Explicitly enable hostname verification.
Use a custom SSLSocketFactory.
Impact:
Man-in-the-Middle attacks
Data interception
Message manipulation
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Sources:
Reported By: github.com
Extra Source Hub:
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