A security flaw was found in the Linux kernel in drivers/tty/n_tty.c which allows local attackers (ones who are able to access pseudo terminals) to lock them up and block further usage of any pseudo terminal devices due to an EXTPROC versus ICANON confusion in TIOCINQ handler.
drivers/tty/n_tty.c in the Linux kernel before 4.14.11 allows local attackers (who are able to access pseudo terminals) to hang/block further usage of any pseudo terminal devices due to an EXTPROC versus ICANON confusion in TIOCINQ.
An upstream patch:
This issue has been addressed in the following products:
Red Hat Enterprise Linux 7
Via RHSA-2019:0831 https://access.redhat.com/errata/RHSA-2019:0831