I didn't find the patched version on LMDE, when I made an update & #aptitude show libgnutls26 the output was Version: 2.12.23-8 (an affected version)
Adding the official Debian repo for Jessie (through the mintUpdate GUI if you prefer) will let you upgrade this package to solve this important security issue:
Code: Select all
deb http://http.us.debian.org/debian/ testing main contrib