https://sourceware.org/ml/libc-alpha/2016-02/msg00416.html
https://www.debian.org/security/2016/dsa-3481
/r/netsec discussion: https://www.reddit.com/r/netsec/comments/462xx0/glibc_getaddrinfo_stackbased_buffer_overflow/
The patch is already out for Debian and some other systems, but has not yet been patched in Tails (which is based on Debian). Other relevant systems, like Whonix and in most cases Qubes, are also affected, along with virtually all other GNU/Linux systems.
This is about as bad as a vulnerability gets. Because so many programs use GlibC, including many daemons, it is strongly recommended to reboot to ensure the update is applied.
Don't be caught on the internet with this thing un-patched if you can help it.
TOR OVER VPN TIME, WINDOWS 7 BROWsING INCOMINg