CrashPython

Category: Misc

Description

I am hosting an uncrashable Python executor API. Crash it to get the flag.

Attachments: dist.zip

Upon examining the source code, it appeared that our user input was being sent to judge0 for Python code execution.

The flag would only be displayed if the following conditions were met:

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1	`status == 11 and message == "Exited with error status 139" and "Segmentation fault" in stderr`

The most straightforward approach was to send a SIGSEV signal to our own process.
We could achieve this by using the following Python code:
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1 2
import os os.kill(os.getpid(), 11)
However, since the word os was banned, we needed to modify the payload to meet the requirements:
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1
__import__(chr(111)+chr(115)).kill(__import__(chr(111)+chr(115)).getpid(), 11)

Flag: grey{pyth0n-cv3-2021-3177_0r_n0t?_cd924ee8df15912dd55c718685517d24}