Canonical published details about ClamAV vulnerabilities, in a security notice, for its Ubuntu 13.04, Ubuntu 12.10, Ubuntu 12.04 LTS, Ubuntu 11.10, and Ubuntu 10.04 LTS operating systems.
According to Canonical, ClamAV could be made to crash or run programs if it opened a specially crafted file.
For example, it was discovered that ClamAV would incorrectly parse a UPX-packed executable, leading to possible inappropriate heap reads.
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 clamav, 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 necessary to implement the changes, but you will need to restart ClamAV.