CVE-2018-8780: Unintentional directory traversal by poisoned NUL byte in Dir

There is an unintentional directory traversal in some methods in Dir. This vulnerability has been assigned the CVE identifier CVE-2018-8780.

Details,, Dir.entries and Dir.empty? accept the path of the target directory as their parameter. If the parameter contains NUL (\0) bytes, these methods recognize that the path is completed before the NUL bytes. So, if a script accepts an external input as the argument of these methods, the attacker can make the unintentional directory traversal.

All users running an affected release should upgrade immediately.

Affected Versions

  • Ruby 2.2 series: 2.2.9 and earlier
  • Ruby 2.3 series: 2.3.6 and earlier
  • Ruby 2.4 series: 2.4.3 and earlier
  • Ruby 2.5 series: 2.5.0 and earlier
  • Ruby 2.6 series: 2.6.0-preview1
  • prior to trunk revision r62989


Thanks to ooooooo_q for reporting the issue.


  • Originally published at 2018-03-28 14:00:00 (UTC)