Canonical published details in a security notice about a SPICE vulnerability in its Ubuntu 13.10 (Saucy Salamander) and Ubuntu 13.04 (Raring Ringtail) operating systems.
According to the company, SPICE could have been made to crash, if it received specially crafted network traffic.
It has been discovered that SPICE incorrectly handled long passwords in SPICE tickets. An attacker could have used this issue to cause the SPICE server to crash, resulting in a denial of service.
For a more detailed description of the security problems, you can see Canonical's security notification.
The security flaws can be fixed if you upgrade your system(s) to the latest libspice-server 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, but this time a system restart will be necessary to implement them.