A security issue affects these releases of Ubuntu and its derivatives:
- Ubuntu 12.04 ESM
Dovecot could be made to expose sensitive information over the network.
- dovecot: IMAP and POP3 email server
USN-3881-1 fixed a vulnerability in Dovecot. This update provides
the corresponding update for Ubuntu 12.04 ESM.
Original advisory details:
It was discovered that Dovecot incorrectly handled client
certificates. A remote attacker in possession of a valid certificate
with an empty username field could possibly use this issue to
impersonate other users.
The problem can be corrected by updating your system to the following