Screen: UTF-8 character handling vulnerability

Background

Screen is a full-screen window manager that multiplexes a physical terminal between several processes, typically interactive shells.

Description

cstone and Richard Felker discovered a flaw in Screen’s UTF-8 combining character handling.

Impact

The vulnerability can be exploited by writing a special string of characters to a Screen window. A remote attacker could cause a Denial of Service or possibly execute arbitrary code with the privileges of the user running Screen through a program being run inside a Screen session, such as an IRC client or a mail client.

Workaround

There is no known workaround at this time.

Resolution

All Screen users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose ">=app-misc/screen-4.0.3"