Vulnerability Note VU#111034

GnuTLS Server Name extension Denial of Service

Overview

A vulnerability exists in GnuTLS that may allow a remote attacker to cause a denial of service.

I. Description

GnuTLS contains a vulnerability in gnults-serv that may result in a denial of service when handling a specially crafted Client Hello message. According to CERT-FI Vulnerability Advisory on GnuTLS:

The problem occurs when gnutls-serv receives Client Hello message which contains Server name extension where the length of the server name list is set to 18 and the data of the server name list consists of 18 zero octets. After receiving this Client Hello message gnutls-serv continues to function normally, but crashes after Finished messages when it tries to pack the session data in function pack_security_parameters() (in lib/gnutls_session_pack.c).

Note that this issue may affect GnuTLS versions prior to 2.2.5 and also affects version 2.3.0.

II. Impact

A remote, unauthorized attacker may be able to cause a denial of service.

III. Solution

Upgrade or Apply Patch

GnuTLS has issued an upgrade and a patch to address this issue. See GnuTLS Security Advisory SA-2008-01 for more information. GnuTLS is included in various Linux and UNIX distributions. Please consult the relevant documentation of your distribution to obtain the appropriate updates.

Systems Affected

Vendor	Status	Date Updated
GnuTLS	Vulnerable	29-May-2008

References

http://www.cert.fi/haavoittuvuudet/advisory-gnutls.html
http://lists.gnu.org/archive/html/gnutls-devel/2008-05/msg00060.html
http://secunia.com/advisories/30287/
http://secunia.com/advisories/30330/

Credit

This issue was reported in GnuTLS Security Advisory SA-2008-01. GnuTLS credits Ossi Herrala and Jukka Taimisto from the CROSS project at Codenomicon Ltd. for reporting this issue.

This document was written by Chris Taschner.

Other Information

Date Public	05/19/2008
Date First Published	05/29/2008 11:46:16 AM
Date Last Updated	05/29/2008
CERT Advisory
CVE Name	CVE-2008-1950
Metric	9.19
Document Revision	3

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