GLSA 200501-23: Exim: Two buffer overflows

Title:Exim: Two buffer overflows
Bugs: #76893


Buffer overflow vulnerabilities, which could lead to arbitrary code execution, have been found in the handling of IPv6 addresses as well as in the SPA authentication mechanism in Exim.


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

Affected packages

Package Vulnerable Unaffected Architecture(s)
mail-mta/exim < 4.43-r2 >= 4.43-r2 All supported architectures


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.


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.


There is no known workaround at this time.


All Exim users should upgrade to the latest version:

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



This GLSA and any updates to it are available for viewing at the Gentoo Security Website:


Security is a primary focus of Gentoo Linux and ensuring the confidentiality and security of our users machines is of utmost importance to us. Any security concerns should be addressed to or alternatively, you may file a bug at


Copyright 2010 Gentoo Foundation, Inc; referenced text belongs to its owner(s). The contents of this document are licensed under the Creative Commons - Attribution / Share Alike license.

Thank you!