The ccid3_hc_tx_getsockopt function in net/dccp/ccids/ccid3.c in the Linux kernel before 3.6 does not initialize a certain structure, which allows local users to obtain sensitive information from kernel stack memory via a crafted application.
https://www.kernel.org/pub/linux/kernel/v3.x/patch-3.6.bz2
https://github.com/torvalds/linux/commit/7b07f8eb75aa3097cdfd4f6eac3da49db787381d