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Category:   Application (Generic)  >   X Vendors:   X.org
(NetBSD Issues Fix) X Buffer Overflow in Processing CID-encoded Type1 Fonts Lets Remote Users Execute Arbitrary Code
SecurityTracker Alert ID:  1016907
SecurityTracker URL:  http://securitytracker.com/id/1016907
CVE Reference:   CVE-2006-3739, CVE-2006-3740   (Links to External Site)
Date:  Sep 22 2006
Impact:   Execution of arbitrary code via network, User access via network
Fix Available:  Yes  Vendor Confirmed:  Yes  
Version(s): 7.1 and prior versions
Description:   A vulnerability was reported in X. A remote authenticated user can execute arbitrary code on the target system.

The software does not properly validate data when parsing CID-encoded Type1 fonts. A remote authenticated user with the ability to set the X server font path can set the path to point to a specially crafted font to trigger an integer overflow in the "type1" module and execute arbitrary code on the target system.

The scan_cidfont() function in 'Type1/scanfont.c' is affected [CVE-2006-3739]. The CIDADM() function in 'Type1/afm.c' is affected [CVE-2006-3740].

The vendor credits iDefense with reporting these vulnerabilities.

Impact:   A remote authenticated user can execute arbitrary code on the target system.
Solution:   NetBSD has released a fix.

The NetBSD advisory is available at:

ftp://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2006-021.txt.asc

Vendor URL:  www.x.org/ (Links to External Site)
Cause:   Boundary error
Underlying OS:  UNIX (NetBSD)
Underlying OS Comments:  4.0_BETA and prior versions

Message History:   This archive entry is a follow-up to the message listed below.
Sep 12 2006 X Buffer Overflow in Processing CID-encoded Type1 Fonts Lets Remote Users Execute Arbitrary Code



 Source Message Contents

Subject:  NetBSD Security Advisory 2006-021: Integer overflows in CID-keyed font



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		 NetBSD Security Advisory 2006-021
		 =================================

Topic:		Integer overflows in CID-keyed font parser

Version:	NetBSD-current:	source prior to September 13, 2006
		NetBSD 4.0_BETA:	affected
		NetBSD 3.1_RC3:		not affected
		NetBSD 3.0.*:		affected
		NetBSD 3.0:		affected
		NetBSD 2.1:		affected
		NetBSD 2.0.*:		affected
		NetBSD 2.0:		affected
		pkgsrc: 		xorg-libs-6.9.0nb8 and earlier
					XFree86-libs-4.4.0nb8 and earlier

Severity:	Potential privilege escalation

Fixed:		NetBSD-current:		September 13, 2006
		NetBSD-4 branch:	September 16, 2006
			(4.0 will include the fix)
		NetBSD-3-0 branch:	September 16, 2006
			(3.0.2 will include the fix)
		NetBSD-3   branch:	September 16, 2006
			(3.1 will include the fix)
		NetBSD-2-1 branch:	September 18, 2006
		NetBSD-2-0 branch:	September 18, 2006
		NetBSD-2   branch:	September 18, 2006
		pkgsrc:			xorg-libs-6.9.0nb9 corrects the issue
					XFree86-libs-4.4.0nb9 corrects the issue

Abstract
========

There are integer overflows present in the CID-keys font parser as 
supplied with both XFree86 and X11R7.0.  This can potentially lead 
to arbitrary code execution.  These vulnerabilities can be triggered 
by a user parsing untrusted CID encoded Type 1 fonts.

These vulnerabilities have been assigned CVE references CVE-2006-3739
and CVE-2006-3740.

Technical Details
=================

There are two separate integer overflows that are present:

* scan_cidfont() function when handling 'CMap' and 'CIDFont' font data.
* CIDAFM() function when handling AFM (Adobe Font Metric) files

Both vulnerabilities can potentially lead to arbitrary code execution.

Solutions and Workarounds
=========================

While X11R7.0 from X.Org is in both the HEAD and netbsd-4 branches it
is currently not integrated fully into the base distribution.  No NetBSD
releases contain X11R7.0 binaries and as such it is not necessary to 
rebuild anything from source.  The instructions below will patch the 
relevant X11R7.0 source files so that if users are experimenting with 
X11R7.0 it will contain the necessary security fixes.

A possible temporary workaround for this issue is to disable Type 1 
fonts in your X Server configuration.  To do this under the Modules 
section of the X Server configuration file comment out the line
containing:
	
	Load "type1"

For X.Org the configuration file will be xorg.conf and for XFree86
it will be XF86config.  This may impact the appearance of applications
run in X Windows.

XFree86-based X servers are included in the NetBSD base distribution,
and will need to be rebuilt.  The following instructions describe how
to upgrade your XFree86 binaries by updating your source tree and
rebuilding and installing a new version of XFree86.

* NetBSD-current:

	Systems running NetBSD-current dated from before 2006-09-13
	should be upgraded to NetBSD-current dated 2006-09-14 or later.

	The following files need to be updated from CVS HEAD:
		xorg/lib/Xfont/src/Type1/afm.c
		xorg/lib/Xfont/src/Type1/scanfont.c
		xorg/lib/Xfont/src/Type1/util.c
		xfree/xc/lib/font/Type1/afm.c 
		xfree/xc/lib/font/Type1/scanfont.c
		xfree/xc/lib/font/Type1/util.c

	To update from CVS, re-build, and re-install XFree86:

		# cd xsrc
		# cvs update xorg/lib/Xfont/src/Type1/afm.c
		# cvs update xorg/lib/Xfont/src/Type1/scanfont.c
		# cvs update xorg/lib/Xfont/src/Type1/util.c
		# cvs update xfree/xc/lib/font/Type1/afm.c 
		# cvs update xfree/xc/lib/font/Type1/scanfont.c
		# cvs update xfree/xc/lib/font/Type1/util.c
		# make build

* NetBSD 3.*:

	Systems running NetBSD 3.* sources dated from before
	2006-09-16 should be upgraded from NetBSD 3.* sources dated
	2006-09-17 or later.

	The following files need to be updated from the
	netbsd-3 or netbsd-3-0 CVS branch:
		xfree/xc/lib/font/Type1/afm.c 
		xfree/xc/lib/font/Type1/scanfont.c
		xfree/xc/lib/font/Type1/util.c

	To update from CVS, re-build, and re-install XFree86:

		# cd xsrc
		# cvs update -r <branch_name> xfree/xc/lib/font/Type1/afm.c
	 	# cvs update -r <branch_name> \
			xfree/xc/lib/font/Type1/scanfont.c
		# cvs update -r <branch_name> xfree/xc/lib/font/Type1/util.c
		# make build

* NetBSD 2.*:

	Systems running NetBSD 2.* sources dated from before
	2006-09-18 should be upgraded from NetBSD 2.* sources dated
	2006-09-19 or later.

	The following files need to be updated from the
	netbsd-2, netbsd-2-0 or netbsd-2-1 CVS branch:
		xfree/xc/lib/font/Type1/afm.c 
		xfree/xc/lib/font/Type1/scanfont.c
		xfree/xc/lib/font/Type1/util.c

	To update from CVS, re-build, and re-install XFree86:

		# cd xsrc
		# cvs update -r <branch_name> xfree/xc/lib/font/Type1/afm.c
	 	# cvs update -r <branch_name> \
			xfree/xc/lib/font/Type1/scanfont.c
		# cvs update -r <branch_name> xfree/xc/lib/font/Type1/util.c
		# make build


Thanks To
=========

iDefense for co-ordinating the disclosure of this issue.


Revision History
================

	2006-09-21	Initial release


More Information
================

Advisories may be updated as new information becomes available.
The most recent version of this advisory (PGP signed) can be found at 
  ftp://ftp.NetBSD.org/pub/NetBSD/security/advisories/NetBSD-SA2006-021.txt.asc

Information about NetBSD and NetBSD security can be found at
http://www.NetBSD.org/ and http://www.NetBSD.org/Security/.


Copyright 2006, The NetBSD Foundation, Inc.  All Rights Reserved.
Redistribution permitted only in full, unmodified form.

$NetBSD: NetBSD-SA2006-021.txt,v 1.4 2006/09/21 20:18:29 adrianp Exp $

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