CVE 2011-3000
Mozilla Firefox before 3.6.23 and 4.x through 6, Thunderbird before 7.0, and SeaMonkey before 2.4 do not properly handle HTTP responses that contain multiple Location, Content-Length, or Content-Disposition headers, which makes it easier for remote attackers to conduct HTTP response splitting attacks via crafted header values.
See the 
CVE page on Mitre.org
for more details.
