In a security notice, Canonical has published details about libxml2 vulnerabilities for its Ubuntu 13.04, Ubuntu 12.10, Ubuntu 12.04 LTS, and Ubuntu 10.04 LTS operating systems.According to Canonical, USN-1904-1 fixed several vulnerabilities in libxml2, but this update caused a regression for certain users.
For example, it was discovered that libxml2 incorrectly handled documents that end abruptly. If a user or automated system were tricked into opening a specially crafted document, an attacker could possibly cause libxml2 to crash, resulting in a denial of service.
For a more detailed description of the security problems, you can visit Canonical's security notification.
The security flaws can be fixed if you upgrade your system(s) to the latest libxml2 package specific to each distribution. To apply the update, run the Update Manager application.
In general, a standard system update will make all the necessary changes. A system restart will not be needed to implement the changes.