Upon successful deserialization, the server executes a PowerShell or CMD command. Common observed payloads include:
Most web apps fail via SQLi or XSS. This exploit is different. It leverages a chain of two logical flaws: smartermail 6919 exploit
Build 6919 is part of SmarterMail version 16.x, which includes several exposed .NET remoting endpoints by default on TCP port 17001 . These endpoints—specifically Upon successful deserialization
While full weaponized code is not provided here, the attack flow looked like this: the attack flow looked like this: