Writeup by: Zanderdk

Introduction

On the 2021-01-26 qualy released this article describing a “new” (actually 10 year old) bug in sudo that allows an attacker to do privilege escalation though a heap buffer overflow. Unfortunately they did not release exploit/POC so I decided to build one myself and failed. …

The challenge is a simple HTML file with a keypad that allows you to input 4 digit pin. The file loads main.js and calls Module.ccall('validate') to check the pin.

Upon beautifying the JS we see that it calls run() which in turns runs:

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preRun();
initRuntime();  // => __wasm_call_ctors => …

As a relatively new team based in Denmark, we are currently limiting our recruitment focus to experienced players either based in Denmark, or who otherwise have strong ties to Scandinavia, as well as those who are invited by current team members.

If you are interested in playing with Kalmarunionen, simply write us an …

Kalmarunionen is a Capture The Flag (CTF) team within cybersecurity. We hack stuff and this is our website. Occasionally we also post writeups and tutorials on how we solved different cybersecurity challenges.

You can always check our world ranking here.