Canonical has published in a security notice details about a Libav vulnerability for its Ubuntu 11.10 (Oneiric Ocelot) operating system.
According to Canonical, Libav (multimedia player, server, encoder and transcoder) could have been made to crash or run programs as the users login, if it opened a specially crafted file.
It was discovered that Libav incorrectly handled certain malformed media files. If a user was tricked into opening a crafted media file, an attacker could cause a denial of service via application crash, or possibly execute arbitrary code with the privileges of the user invoking the program.
The security flaws can be fixed if you upgrade your system(s) to the latest libavformat53 and libavcodec53 versions. To apply the update, run the Update Manager application.
In general, a standard system update will make all the necessary changes. A system restart won't be necessary.