tripwire is an open source file integrity checker.
The code that generates email reports contains a format string vulnerability in pipedmailmessage.cpp.
With a carefully crafted filename on a local filesystem an attacker could cause execution of arbitrary code with permissions of the user running tripwire, which could be the root user.
There is no known workaround at this time.
All tripwire users should upgrade to the latest stable version:
# emerge sync
# emerge -pv ">=app-admin/tripwire-2.3.1.2-r1"
# emerge ">=app-admin/tripwire-2.3.1.2-r1"