Georgi Guninski discovered two stack-based buffer overflows. They can not be exploited with the default configuration from the Debian system, though. The Common Vulnerabilities and Exposures project identifies the following problems that are fixed with this update:
When "sender_verify = true" is configured in exim.conf a buffer overflow can happen during verification of the sender. This problem is fixed in exim 4.
When headers_check_syntax is configured in exim.conf a buffer overflow can happen during the header check. This problem does also exist in exim 4.
For the stable distribution (woody) these problems have been fixed in version 3.35-1woody3.
For the unstable distribution (sid) these problems have been fixed in version 3.36-11 for exim 3 and in version 4.33-1 for exim 4.
We recommend that you upgrade your exim package.