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502 Bad Gateway after upgrading Debian to latest version

There is a dash vulnerability on Debian, please following the steps below to check your system:


  1. Log into your server as root

  2. Execute the following command:

env x='() ; echo vulnerable' bash -c "echo this is a test"

3. If the output is "this is a test", that means that your bash needs to be updated. Please refer to your specific OS below and update your system and bash to latest version.


1. Log into your server as root
2. Execute the following command:

export dummy='() ; echo "exploited"'

  1. Enter the following command afterwards:

  2. If the output is "exploited", that means that your bash needs to be updated.


On my Debian, I ran apt-get update && apt-get -y upgrade to update my system to latest version, then found my blog inaccessible, it gave me 502 Bad Gateway error.

I finally figured it out in

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