14 DAY TRIAL // Canonical published details about the NSPR vulnerability in its Ubuntu 13.10, Ubuntu 13.04, Ubuntu 12.10, Ubuntu 12.04 LTS, and Ubuntu 10.04 LTS operating systems.
According to the company, NSPR could be made to crash or to run programs if it received a specially crafted certificate.
It has been discovered that NSPR incorrectly handled certain malformed X.509 certificates. A remote attacker could use a crafted X.509 certificate to cause NSPR to crash, leading to a denial of service, or possibly execute arbitrary code.
For a more detailed description of the problems, you can see Canonical's security notification.
The security flaws can be fixed if you upgrade your system(s) to the latest libnspr4 package specific to each distribution. To apply the patch, run the Update Manager application.
In general, a standard system update will make all the necessary changes and you will have to restart the system.