Unpatched Firefox flaw may expose users.
Published: September 9, 2005, 3:53 AM PDT
By Joris Evers
Staff Writer, CNET News.com
http://news.com.com/Unpatched+Firefox+flaw+may+expose+users/2100-1002_3-5856
201.html?part=rss&tag=5856201&subj=news

A new, unpatched flaw in that affects all versions of Firefox could let
attackers surreptitiously run malicious code on users' PCs, a security
researcher has warned.

The problem lies in the way Firefox handles Web links that are overly long
and contain dashes, security researcher Tom Ferris said in an interview via
instant messaging late Thursday.

He posted an advisory and a proof of concept to the Full Disclosure security
mailing list and to his Security Protocols Web site.

The security vulnerability is a buffer overflow flaw that "allows for an
attacker to remotely execute arbitrary code" on a vulnerable PC, Ferris
said. An attacker could host a Web site containing the malicious code to
exploit the flaw, he said. Though his proof of concept only crashes Firefox,
Ferris claims he has been able to tweak it to run code.

Buffer overflows are a commonly exploited security problem. They occur when
a program allows data to be written beyond the allocated end of a buffer in
memory. A computer can be made to execute potentially malicious code by
feeding in extra data that is designed to flood the buffer.

Ferris reported the bug to the Mozilla Foundation on Sunday, intending to go
through the organization's bug-reporting process, he said. However, in an
example of the uneasy alliance between security researchers and software
makers, he decided to publicly disclose the flaw after a run-in with Mozilla
staff, he said.

Mozilla, which coordinates development of Firefox and distributes the
software, could not immediately comment on the flaw disclosure. However, a
source close to the organization confirmed that Ferris had filed several bug
reports, including this specific one.

Since the debut of Firefox 1.0 in November, usage of the open source browser
has grown. Security has been a main selling point for Firefox over
Microsoft's Internet Explorer, which has begun to see its market share dip
slightly--for the first time in years.

However, Firefox has had its own security woes. Several serious holes in the
browser have been plugged since its official release and experts have said
that safe Web browsers don't exist.

The public bug disclosure comes just as Mozilla released the first beta of
Firefox 1.5. The final release of the next Firefox update, which includes
security enhancements, is due by year's end, according to the Firefox road
map.

Ferris has found bugs in Microsoft software before, including a
yet-unpatched flaw in Internet Explorer that Microsoft still has under
investigation.

Earlier this month Microsoft credited Ferris with reporting a bug in a
Windows feature called the Remote Desktop Protocol that could allow an
attacker to remotely restart Windows systems.





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