Mozilla Firefox "Host:" Buffer Overflow

[Tom Ferris <tommy () security-protocols com>]

Mozilla Firefox "Host:" Buffer Overflow

Release Date:
September 8, 2005

Date Reported:
September 4, 2005

Severity:
Critical

Vendor:
Mozilla

Versions Affected:
Firefox Win32 1.0.6 and prior
Firefox Linux 1.0.6 and prior
Firefox 1.5 Beta 1 (Deer Park Alpha 2)

Overview:

A buffer overflow vulnerability exists within Firefox version 1.0.6 and all 
other prior versions which allows for an attacker to remotely execute arbitrary 
code on an affected host.

Technical Details:
The problem seems to be when a hostname which has all dashes causes the 
NormalizeIDN call in nsStandardURL::BuildNormalizedSpec to return true, but is 
sets encHost to an empty string.  Meaning, Firefox appends 0 to approxLen and 
then appends the long string of dashes to the buffer instead.  The following 
HTML code below will reproduce this issue:

<A HREF=https:--------------------------------------------- >

Simple, huh? ;-]

Vendor Status:
Mozilla was notified, and im guessing they are working on a patch. Who knows 
though?

Discovered by:
Tom Ferris

Related Links:
www.security-protocols.com/firefox-death.html
www.security-protocols.com/advisory/sp-x17-advisory.txt
www.security-protocols.com/modules.php?name=News&file=article&sid=2910

Greetings:
chico, modify, ac1djazz, dmuz, aempirei, Daniel Sergile, tupac shakur, and the 
rest of the angrypacket krew.

Copyright (c) 2005 Security-Protocols.com

Thanks,

Tom Ferris
Researcher
www.security-protocols.com
Key fingerprint = 0DFA 6275 BA05 0380 DD91  34AD C909 A338 D1AF 5D78