CVE-2020-10933: Heap exposure vulnerability in the socket library

A heap exposure vulnerability was discovered in the socket library. This vulnerability has been assigned the CVE identifier CVE-2020-10933. We strongly recommend upgrading Ruby.


When BasicSocket#recv_nonblock and BasicSocket#read_nonblock are invoked with size and buffer arguments, they initially resize the buffer to the specified size. In cases where the operation would block, they return without copying any data. Thus, the buffer string will now include arbitrary data from the heap. This may expose possibly sensitive data from the interpreter.

This issue is exploitable only on Linux. This issue had been since Ruby 2.5.0; 2.4 series is not vulnerable.

Affected versions

  • Ruby 2.5 series: 2.5.7 and earlier
  • Ruby 2.6 series: 2.6.5 and earlier
  • Ruby 2.7 series: 2.7.0
  • prior to master revision 61b7f86248bd121be2e83768be71ef289e8e5b90


Thanks to Samuel Williams for discovering this issue.


  • Originally published at 2020-03-31 12:00:00 (UTC)