A timing attack was found in the way NSS generated DSA signatures. A man-in-the-middle attacker could use this flaw during DSA signature generation to recover the private key.
For Debian 7 Wheezy, these problems have been fixed in version 2:3.26-1+debu7u12.
We recommend that you upgrade your nss packages.
Further information about Extended LTS security advisories can be found at: https://deb.freexian.com/extended-lts/