Profile for joern
About joern
Fields
- Website
- https://0day.click
- Threema
- https://threema.id/K8J68WTX
Bio
Your mom's favorite hacker!
My other account is @joernchen
- Joined
- Posts
- 686
- Followed by
- 1129
- Following
- 261
Stats
Recent public posts
exclude boosts@joern CVSS? Not even once.
Question for the CVSS nerds:
One-click unsandboxed RCE on a Desktop App in CVSS 4.0 --> Subsequent System Impact Metrics are what exactly?
Anyone in Berlin from whom I can borrow an RTL-SDR (USB, ideally with antenna)? Ideally in West Berlin, near U7 or near Schlesi :)
When you instruct your LLM, why is it:
“make no mistakes!”
and not:
“good vibes only!”
Thanks so much to everyone who showed up on the weekend in Berlin to say goodbye to FX.
“Burning bridges where we can” - this is the original Phenoelit slogan. Yet, while FX for sure burned some network bridges, he did quite the opposite for the hacking community. FX built bridges between people wherever he could. He created something way bigger than himself which we all are part of.
Each one who joined us in Berlin carries a piece of his legacy. You were there because he left something with you. We know there are many who couldn't make it in person, and they too carry his spirit with them.
FX is gone.
But the spirit lives on.
I finally managed to write something about my recently deceased dear friend Felix 'Fx' Lindner.
i look forward to AI finding an 0day and providing a patch that contains a backdoor for a supply chain attack.
LLMs now do the busywork of finding amazing vulnerabilities for everyone willing to spend the tokens.
But hacking still isn't dead:
We haven't at all solved the underlying problems which come with writing and shipping code.
You still need to understand what you're looking at and what you are operating.
The LLM platforms themselves are a exquisite target for hacking^Wcreative use of the technology.
Now when everyone can pull a CVE or two out of thin silicon and a few kWh of electricity the art of hacking might need adopt and maybe reshape a little but at its core the mind- and skillset will stay as relevant as it always was.
In that sense: keep hacking, keep exploring, break some stuff.
If your Open Source project sees a steep increase in number of high quality security reports (mostly done with AI) right now (#curl, Linux kernel, glibc confirmed) please tell me the name of this project.
(I'd like to make a little list for my coming talk on this.)
Letting Gemini proof read my Claude Code vulnerability write ups. 🤡
RIP FX
We collected some texts from the community in memory of FX. You can find them here https://phenoelit.de/fx.html
@joern RIP FX. Lets remember him in the good old days https://media.ccc.de/search?p=FX
Lands of Packets
TTL exceeded.
I would like to collect texts from the scene about FX in his memory. A collection of obituaries that will then be posted on phenoelit.de.
If anyone would like to contribute, please contact me.
Mail: joernchen@phenoelit.de
Signal: jrn.07
:(
Due to $reasons I came across this blogpost https://www.elttam.com/blog/env/ about turning ENV variables into code execution which is nice. But the Python vector is depending on Perl, I didn't like that :P.
Digging a bit deeper in the code often helps, so it did this time:
Looking at https://github.com/python/cpython/blob/d73634935cb9ce00a57dcacbd2e56371e4c18451/Lib/webbrowser.py#L51-L52 I could simplify the payload to:
PYTHONWARNINGS='module::antigravity.' BROWSER='sh -c id #%s' python whatever.py
Wheeee my presentation on parser differentials made it on the Top Ten Web Hacking Techniques of 2025
https://portswigger.net/research/top-10-web-hacking-techniques-of-2025
The voting has concluded, and we're thrilled to announce the top ten web hacking techniques of 2025! Massive thanks to everyone in the community for sharing their hard-earned discoveries, plus the panel and everyone who nominated or voted! https://portswigger.net/research/top-10-web-hacking-techniques-of-2025

