It was discovered that the GnuTLS certificate verification methods implemented in Curl did not check for expiration and activation dates. When performing validations, tools using libcurl3-gnutls would incorrectly allow connections to sites using expired certificates.
The problem can be corrected by updating your system to the following package versions:
17 July 2007
A security issue affects these releases of Ubuntu and its derivatives:
It was discovered that the GnuTLS certificate verification methods implemented in Curl did not check for expiration and activation dates. When performing validations, tools using libcurl3-gnutls would incorrectly allow connections to sites using expired certificates.
The problem can be corrected by updating your system to the following package versions:
To update your system, please follow these instructions: https://wiki.ubuntu.com/Security/Upgrades.
After a standard system upgrade you need to reboot your computer to effect the necessary changes.