Suppose I own the whynot.com domain. Can I request a certificate for google.com\0x.whynot.com ?

1 Answer 1


Since google.com\0x.whynot.com is not a valid hostname you should not by able to get a certificate for it. But it was possible once to misuse null characters like you attempt. For more details see Black Hat 2009: Breaking SSL With Null Characters.

  • Thank you. It's not possible because how the SSL name encoding or browser's way of interpreting strings was changed or because CA's validate the name more accurately ? from the linked page "The CA ignores the subdomain"
    – cyzczy
    Apr 7, 2017 at 8:45
  • 2
    @adam86: both the validation in the browsers and the CA's was enhanced to make sure to accept only valid names. Apr 7, 2017 at 9:20

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