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Grub2 overflow caused very funny vulnerability
  • Vitaliy_KiselevVitaliy_Kiselev

    Short version.

    For many versions and configurations just pressing backspace 28 times and enter instead of password you get rescue shell (with consequences if you have bad intentions).

    Longer version

    Pressing backspace without proper string length check cause stack damage. If you press it enough same happens with return address. As result CPU jumps to 0 address (IVT table) after pressing enter.
    This cause memory copy that repeats few times. In result we will get to retw instruction that will cause jump to address of rescue shell.

    Very long version at http://hmarco.org/bugs/CVE-2015-8370-Grub2-authentication-bypass.html

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