Type Confusion exists in _cancel_eval Ruby’s TclTkIp class method. Attacker passing different type of object than String as “retval” argument can cause arbitrary code execution. References: http://www.talosintelligence.com/reports/TALOS-2016-0031/
Upstream patches: https://github.com/ruby/tk/commit/ebd0fc80d62eeb7b8556522256f8d035e013eb65 https://github.com/ruby/tk/commit/d098136e3f62a4879a7d7cd34bbd50f482ba3331
This vulnerability requires that the attacker can execute arbitrary Ruby code under elevated privileges, which is already a bad idea. The "cancel_eval" function is only available when tcl-8.6 is present. Red Hat Enterprise Linux presently only ships tcl<=8.5, so this vulnerability can not be exploited.
> This vulnerability requires that the attacker can execute arbitrary Ruby code under elevated privileges, which is already a bad idea. The 'tk' module will only load from within an X session (eg $DISPLAY pointing to a valid X server), making conditions for exploitation even more unlikely.
Statement: Red Hat Product Security has rated this issue as having Moderate security impact. This issue is not currently planned to be addressed in future updates. For additional information, refer to the Issue Severity Classification: https://access.redhat.com/security/updates/classification/.