Vulnerability Note VU#423396

X.509 certificate verification may be vulnerable to resource exhaustion

Overview

Some applications that perform X.509 certificate verification may be vulnerable to signature processing problems that lead to resource exhaustion. This vulnerability may cause a denial of service.

I. Description

Included in X.509 certificates are public keys used for digital signature verification. Choosing very large values for the public exponent and public modulus associated with an RSA public key may cause the verification of that key to require large amounts of system resources. According to NISCC:

...by choosing much larger values for [the public exponent and the public modulus], it may be possible to cause the verification process to consume large amounts of system resources and hence result in a denial-of-service condition.

This vulnerability can be triggered by sending a message signed using specially crafted RSA keys to affected products. A number of different products that verify RSA signatures may be vulnerable to this issue. Please see the Systems Affected section of this document for specific product information.

II. Impact

A remote, unauthenticated attacker could consume large amounts of system resources on an affected device, thereby creating a denial of service.

III. Solution

Upgrade or apply a patch from the vendor

Patches have been released to address this issue. See the systems affected section of this document for information about specific vendors.

Systems Affected

Vendor	Status	Date Notified
Apple Computer, Inc.	Vulnerable	4-Dec-2006
Avaya, Inc.	Vulnerable	10-Nov-2006
Cisco Systems, Inc.	Vulnerable	13-Nov-2006
Debian GNU/Linux	Vulnerable	2-Oct-2006
FreeBSD, Inc.	Vulnerable	28-Sep-2006
Gentoo Linux	Vulnerable	19-Jan-2007
GnuTLS	Vulnerable	28-Sep-2006
Hewlett-Packard Company	Vulnerable	19-Jan-2007
Mandriva, Inc.	Vulnerable	2-Oct-2006
OpenBSD	Vulnerable	23-Oct-2006
OpenPKG	Vulnerable	2-Oct-2006
OpenSSL	Vulnerable	28-Sep-2006
Oracle Corporation	Vulnerable	17-Jan-2007
Red Hat, Inc.	Vulnerable	2-Oct-2006
rPath	Vulnerable	6-Oct-2006
Slackware Linux Inc.	Vulnerable	2-Oct-2006
Sun Microsystems, Inc.	Vulnerable	10-Nov-2006
SUSE Linux	Vulnerable	2-Oct-2006
Trustix Secure Linux	Vulnerable	2-Oct-2006
Ubuntu	Vulnerable	28-Sep-2006
VMware	Vulnerable	19-Jan-2007

References

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-2940
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2004-2531
http://www.hornik.sk/SA/SA-20040802.txt
http://www.gnu.org/software/gnutls/
http://www.securitytracker.com/alerts/2004/Aug/1010838.html
http://www.niscc.gov.uk/niscc/docs/re-20060928-00661.pdf?lang=en
http://www.openssl.org/news/secadv_20060928.txt
http://secunia.com/advisories/23280/
http://secunia.com/advisories/23309/
http://secunia.com/advisories/23351/
http://www.securityfocus.com/bid/22083
http://sunsolve.sun.com/search/document.do?assetkey=1-26-102668-1

Credit

NISCC credits Dr. Stephen N. Henson for reporting this vulnerability. This issue was originally reported in GnuTLS by Patrik Hornik.

This document was written by Chris Taschner.

Other Information

Date Public:	2004-08-02
Date First Published:	2006-09-28
Date Last Updated:	2007-02-09
CERT Advisory:
CVE-ID(s):	CVE-2006-2940
NVD-ID(s):	CVE-2006-2940
US-CERT Technical Alerts:
Metric:	7.92
Document Revision:	62

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Produced 2006 by US-CERT, a government organization
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