Hi,
if we assume for simplicity that every relay running Linux that has not rebooted since 2016-02-16 is vulnerable to CVE-2015-7547, than these are the current stats (optimistic, because we assume that everyone that rebooted did also update).
Vulnerable relays:
+------------+------------------+-----------------+ | cwfraction | guardprobability | exitprobability | +------------+------------------+-----------------+ | 0.586 | 0.639 | 0.518 | +------------+------------------+-----------------+ (1=100%)
Apply patches and reboot.
Debian https://www.debian.org/security/2016/dsa-3481
RHEL/CentOS https://rhn.redhat.com/errata/RHSA-2016-0176.html