courier - programming error

A problem has been discovered in the Courier Mail Server. DNS
failures were not handled properly when looking up Sender Policy
Framework (SPF) records, which could allow attackers to cause memory
corruption. The default configuration on Debian has SPF checking
disabled, so most machines are not vulnerable. This is explained in
the “courier” manpage, section SENDER POLICY FRAMEWORK KEYWORDS.

The old stable distribution (woody) is not affected by this problem.

For the stable distribution (sarge) this problem has been fixed in
version 0.47-4sarge1.

For the unstable distribution (sid) this problem has been fixed in
version 0.47-6.

We recommend that you upgrade your courier-mta package.