The MITRE CVE dictionary describes this issue as:
The import_request_variables function in PHP 4.0.7 through 4.4.6, and 5.x before 5.2.2, when called without a prefix, does not prevent the (1) GET, (2) POST, (3) COOKIE, (4) FILES, (5) SERVER, (6) SESSION, and other superglobals from being overwritten, which allows remote attackers to spoof source IP address and Referer data, and have other unspecified impact. NOTE: it could be argued that this is a design limitation of PHP and that only the misuse of this feature, i.e. implementation bugs in applications, should be included in CVE. However, it has been fixed by the vendor.
Find out more about CVE-2007-1396 from the
MITRE CVE dictionary dictionary and
NIST NVD.
Statement
Red Hat does not consider this to be a security vulnerability. Using import_request_variables() is generally a discouraged practice and it is improper use that can lead to security problems, not flaw of PHP itself.