Bypassing SSL Validation in a Java Application via Truststore

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This article details bypassing SSL validation in the Java-based CTF thick client app “Cosmic Snap Java Edition” using Burp Suite to intercept HTTPS traffic. The method integrates Burp’s CA certificate into the app’s custom truststore.

Download the app from: https://github.com/thecybersandeep/Cosmic-Snapshot-Java-Edition

🔐 What is a Truststore?

A Java truststore is a keystore file storing trusted SSL/TLS certificates. The JVM uses it to verify remote certificates.

Default truststore:
<JAVA_HOME>/jre/lib/security/cacerts

Custom .jks truststores can override defaults.

🎯 Challenge

“Cosmic Snapshot” uses a custom truststore (cosmic.jks) for SSL validation, blocking Burp Suite interception unless Burp’s CA certificate is trusted.

When sending normal requests from Cosmic Snap Java Edition with a proxy configured (via app settings or Proxifier), an SSL error occurs in Burp Suite due to the app’s strict cosmic.jks truststore.

Figure 1: Normal request captured from the Cosmic Snapshot — Java Edition app.