Aptdaemon 0.43 and earlier in Ubuntu 11.04, 11.10, and 12.04 LTS does not authenticate packages when the transaction is not simulated, which allows remote attackers to install arbitrary packages via a man-in-the-middle attack.
The Apport hook in Update Manager as used by Ubuntu 12.04 LTS, 11.10, and 11.04 uploads certain system state archive files when reporting bugs to Launchpad, which allows remote attackers to read repository credentials by viewing a public bug report.
The Transparent Inter-Process Communication (TIPC) functionality in Linux kernel 2.6.16-rc1 through 2.6.33, and possibly other versions, allows local users to cause a denial of service (kernel OOPS) by sending datagrams through AF_TIPC before entering network mode, which triggers a NULL pointer dereference.
The distcheck rule in dist-check.mk in GNU coreutils 5.2.1 through 8.1 allows local users to gain privileges via a symlink attack on a file in a directory tree under /tmp.