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Aaditya Purani Profile picture
Aaditya Purani
@aaditya_purani
SecEng @awscloud. CTFs with @pb_ctf. DEFCON & BHUSA speaker. Passionate about everything tech. My opinions are my own. Ex-@Tesla @bishopfox @PaloAltoNtwks
Dec 18, 2021 • 5 tweets • 2 min read
Is anyone able to reliably "crash/kill" the application completely using this log4j DoS hype ride?

So far I'm yet to reproduce a weaponizable damage outside of denying logging. (IllegalStateException) 🤔

Expansion payload (10k reps or more) will do StackOverflow exception (1/n) Along with @0xsapra , we reproduced it against 2.14 giving it the priority as it has lookups enabled by default.

To weaponize, the goal was to kill/crash the app not just throw Exception.

We tried multiple payload deliveries-
1.) GET request (max size 2048):
Payload used was
Dec 13, 2021 • 5 tweets • 3 min read
How to attack any JDK version for log4j "without" guessing classpath on server?

Try to exfiltrate the class path using ${sys:java.class.path} or ${env:CLASSPATH}.

What if it fails? Don't forget java. net.URL is serializable! You can bruteforce ClassName

github.com/BishopFox/Gadg… So, the idea is to retrieve the remote Java ClassPaths using GadgetProbe.

It is trivial to create a serializable payload by iterating through commonly used classname signatures and use github.com/pimps/JNDI-Exp… to serve it.

This way you will know libraries used on classpath