full-disclosure - Re: [FDSA] Sort - Critical Format String Vulnerability

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Date: Fri, 18 Jan 2008 08:45:41 +0100
From: Tonnerre Lombard <tonnerre.lombard@...roup.ch>
To: "Fredrick Diggle" <fdiggle@...il.com>
Cc: full-disclosure@...ts.grok.org.uk
Subject: Re: [FDSA] Sort - Critical Format String
 Vulnerability

Salut, Fredrick,

On Thu, 17 Jan 2008 12:05:13 -0600 "Fredrick Diggle"
<fdiggle@...il.com> wrote:
> The following output shows a manafestation of this vulnerability:
> 
> C:\>sort AAAA%x.%x.%x.%x
> AAAA7c812f39.0.0.41414141The system cannot find the file specified.

This is actually confirmed on Windows 2000 and XP.

> This vulnerability can be trivially exploited to execute arbitrary
> code on the computer machine.

There I don't agree however, it is a simple memory reading
vulnerability.

> The following command line will use sort.exe to execute the windows
> calculator.
> 
> C:\>sort CALC.EXE%x%x%x%n | calc

That's not very surprising since you pipe into the calculator so it is
spawned by the shell.

> Severity: Quite High

There I don't agree. In theory, there should not be anything important
in the memory of the sort process which is not already known to the
user executing it anyway. It is clearly a bug though, and wants to be
fixed. So congratulations to a working, though overdramatizised,
discovered format string vulnerability.

				Tonnerre
-- 
SyGroup GmbH
Tonnerre Lombard

Solutions Systematiques
Tel:+41 61 333 80 33		Güterstrasse 86
Fax:+41 61 383 14 67		4053 Basel
Web:www.sygroup.ch		tonnerre.lombard@...roup.ch

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