description
Exploit a 2021 Kernel vulnerability in Ubuntu to become root almost instantly!

🖥 OverlayFS: CVE-2021-3493

{% embed url="https://tryhackme.com/room/overlayfs" %} https://tryhackme.com/room/overlayfs {% endembed %}

Room Attributes	Value
Subscription Required	False [Free]
Type	Walkthrough
Difficulty	Info
Tags	PrivEsc, Linux, Ubuntu, Kernel, CVE-2021-3493

Task 1 - What is OverlayFS?

I have a very rough overview of what OverlayFS is

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Task 2 - CVE-2021-3493 - OverlayFS Exploit

Deploy the machine with the Start Machine button in this task and wait up to 2 minutes for the VM to boot.

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SSH into the machine with the credentials provided in the task text.

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Grab the source code for the exploit from SSD-Disclosure here and save it as exploit.c on the target machine.

{% hint style="warning" %} HINT: Perhaps the easiest way is copy/pasting the code into a text editor like Nano or Vim! {% endhint %}

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Compile the exploit with gcc. If you're finding this difficult, a command is given in the hints.

{% hint style="warning" %} HINT: gcc -o exploit exploit.c {% endhint %}

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Run your compiled exploit, and get root! What's the flag in /root/?

Reveal Flag 🚩

🚩thm{27aaa5865a52dcd4cb04c0e0a2d39404}

Task 3 - Further reading

Hope you've enjoyed this short room.

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