The MITRE CVE dictionary describes this issue as:
Argument injection vulnerability in Mozilla Firefox before 2.0.0.5, when running on systems with Thunderbird 1.5 installed and certain URIs registered, allows remote attackers to conduct cross-browser scripting attacks and execute arbitrary commands via shell metacharacters in a mailto URI, which are inserted into the command line that is created when invoking Thunderbird.exe, a similar issue to CVE-2007-3670.
Find out more about CVE-2007-4038 from the
MITRE CVE dictionary dictionary and
NIST NVD.
Statement
Not vulnerable. This issue does not affect the versions of Firefox or Thunderbird as shipped with Red Hat Enterprise Linux.