All of Dapper, Hardy, Intrepid and Jaunty got kernel updates today due to multiple vulnerabilities found in kernels 2.6.15, 2.6.24, 2.6.27 and 2.6.28.

Detailed description of the vulnerabilities can be found at USN-852-1.

In short, the list of faulty components include:

AppleTalk

eCryptFS

NFSv4

SCSI driver

KVM

UDP stack

and a bunch of other drivers...

ubuntuupdates.org has the full list of kernel versions available for the 4 most recent Ubuntu releases. Look for the 'linux' package or directly go to the linux package versions page.

As an example, the new kernel for Jaunty is 2.6.28-16.