Vulnerability Instance

This module exploits a heap buffer overflow within versions of Exim prior to
          version 4.69. By sending a specially crafted message, an attacker can corrupt the
          heap and execute arbitrary code with the privileges of the Exim daemon.

          The root cause is that no check is made to ensure that the buffer is not full
          prior to handling '%s' format specifiers within the 'string_vformat' function.
          In order to trigger this issue, we get our message rejected by sending a message
          that is too large. This will call into log_write to log rejection headers (which
          is a default configuration setting). After filling the buffer, a long header
          string is sent. In a successful attempt, it overwrites the ACL for the 'MAIL
          FROM' command. By sending a second message, the string we sent will be evaluated
          with 'expand_string' and arbitrary shell commands can be executed.

          It is likely that this issue could also be exploited using other techniques such
          as targeting in-band heap management structures, or perhaps even function pointers
          stored in the heap. However, these techniques would likely be far more platform
          specific, more complicated, and less reliable.

          This bug was original found and reported in December 2008, but was not
          properly handled as a security issue. Therefore, there was a 2 year lag time
          between when the issue was fixed and when it was discovered being exploited
          in the wild. At that point, the issue was assigned a CVE and began being
          addressed by downstream vendors.

          An additional vulnerability, CVE-2010-4345, was also used in the attack that
          led to the discovery of danger of this bug. This bug allows a local user to
          gain root privileges from the Exim user account. If the Perl interpreter is
          found on the remote system, this module will automatically exploit the
          secondary bug as well to get root.

Reliability:
  - unknown-reliability
Stability:
  - unknown-stability
SideEffects:
  - unknown-side-effects