On November 5, in a security notice Canonical published details about Munin vulnerabilities for its Ubuntu 12.10, Ubuntu 12.04 LTS, Ubuntu 11.10, Ubuntu 11.04, and Ubuntu 10.04 LTS operating systems.
According to Canonical, several security issues were fixed in Munin. It was discovered that the Munin qmailscan plugin incorrectly handled temporary files and plugin state file permissions.
A local attacker could have used this issue to overwrite arbitrary files or to escalate privileges to root.
For a more detailed description of the security problems, you can visit Canonical's security notification.
Users can simply fix the security flaws by upgrading the operating systems to the latest munin package, specific to each distribution.
A normal system update, executed with the Update Manager, will implement all the necessary changes. A complete system restart is not necessary.