Exim: Two buffer overflows

Background

Exim is an highly configurable message transfer agent (MTA) developed at the University of Cambridge.

Description

Buffer overflows have been found in the host_aton() function (CAN-2005-0021) as well as in the spa_base64_to_bits() function (CAN-2005-0022), which is part of the SPA authentication code.

Impact

A local attacker could trigger the buffer overflow in host_aton() by supplying an illegal IPv6 address with more than 8 components, using a command line option. The second vulnerability could be remotely exploited during SPA authentication, if it is enabled on the server. Both buffer overflows can potentially lead to the execution of arbitrary code.

Workaround

There is no known workaround at this time.

Resolution

All Exim users should upgrade to the latest version:

 # emerge --sync
 # emerge --ask --oneshot --verbose ">=mail-mta/exim-4.43-r2"