CVE 2012-1172
The file-upload implementation in rfc1867.c in PHP before 5.4.0 does not properly handle invalid [ (open square bracket) characters in name values, which makes it easier for remote attackers to cause a denial of service (malformed $_FILES indexes) or conduct directory traversal attacks during multi-file uploads by leveraging a script that lacks its own filename restrictions.
See the 
CVE page on Mitre.org
for more details.
