From Ludwig Nussel[1]

Hi,

Connections in NetworkManager 0.9 store path names to certificates and
key files. That means NM (or rather wpa_supplicant which gets
configured by NM) accesses the user's files as root. A user who is
allowed to add connections (default for locally logged in users) may
specify arbitrary file names. NM happily accepts files of any other
user, including root and even device files. Fortunately it's read
access only.

The safe approach would be to stream the actual content of the
certificate and key files to NM and have NM store that directly.
In fact NM 0.7 does just that for system connections (but forgets to
store the key so those connections won't actually work).

NM 0.6 is also affected.

Reproducer for NM 0.9 attached, you need to edit the file names and
then run e.g.
$ nmw.py new wlan0 yourssid

cu
Ludwig

[1] http://seclists.org/oss-sec/2012/q1/513