CVE 2012-0214

The pkgAcqMetaClearSig::Failed method in apt-pkg/acquire-item.cc in Advanced Package Tool (APT) 0.8.11 through 0.8.15.10 and 0.8.16 before 0.8.16~exp13, when updating from repositories that use InRelease files, allows man-in-the-middle attackers to install arbitrary packages by preventing a user from downloading the new InRelease file, which leaves the original InRelease file active and makes it more difficult to detect that the Packages file is modified and unsigned.

See the CVE page on Mitre.org for more details.