fs/proc/base.c in the Linux kernel before 2.6.39.4 does not properly restrict access to /proc/#####/io files, which allows local users to obtain sensitive I/O statistics by polling a file, as demonstrated by discovering the length of another user's password.
Exploitability
AV:LAC:LAu:NImpact
C:PI:NA:N2.1/AV:L/AC:L/Au:N/C:P/I:N/A:N