Vulnerability Note VU#377812

Mozilla Network Security Services (NSS) fails to properly process malformed SSLv2 server messages

Overview

A vulnerability in the way Mozilla Network Security Services (NSS) handles malformed SSLv2 server messages may lead to execution of arbitrary code.

I. Description

The SSLv2 protocol uses a client master key to generate all subsequent session keys. The client master key is created using a public key recieved from the server during phase one of the SSL handshake. Mozilla NSS library contains a vulnerability in the way malformed SSLv2 server messages related to the public key are handled that may result in a buffer overflow. According to the Mozilla Foundation Security Advisory 2007-06:

SSL clients such as Firefox and Thunderbird can suffer a buffer overflow if a malicious server presents a certificate with a public key that is too small to encrypt the entire "Master Secret". Exploiting this overflow appears to be unreliable but possible if the SSLv2 protocol is enabled.

Note that this vulnerability may affect any application that uses the Mozilla NSS library.

II. Impact

A remote, unauthenticated attacker may be able to execute arbitrary code with the privileges of the user who is running the vulnerable application or cause a denial of service.

III. Solution

Apply an update

According to the Mozilla Foundation Security Advisory 2007-06, this vulnerability is addressed in Firefox 2.0.0.2, Firefox 1.5.0.10, SeaMonkey 1.0.8, and NSS 3.11.5.

Disable SSLv2

Disabling support for the SSLv2 protocol appears to prevent exploitation of this vulnerability. Instructions for disabling the SSLv2 protocol support in Firefox and Thunderbird can be found in the Mozilla Foundation Security Advisory 2007-06.

Systems Affected

Vendor	Status	Date Notified
Fedora Project	Vulnerable	7-Mar-2007
Gentoo Linux	Vulnerable	5-Apr-2007
Mandriva, Inc.	Vulnerable	7-Mar-2007
Mozilla	Vulnerable	27-Feb-2007
Red Hat, Inc.	Vulnerable	7-Mar-2007
rPath	Vulnerable	7-Mar-2007
Slackware Linux Inc.	Vulnerable	5-Apr-2007
Sun Microsystems, Inc.	Vulnerable	5-Apr-2007
SUSE Linux	Vulnerable	7-Mar-2007
Ubuntu	Vulnerable	7-Mar-2007

References

Credit

This vulnerability was reported in Mozilla Foundation Security Advisory 2007-06. Mozilla credits iDefense with reporting this issue.

This document was written by Chris Taschner.

Other Information

Date Public:	2007-02-23
Date First Published:	2007-03-07
Date Last Updated:	2007-04-05
CERT Advisory:
CVE-ID(s):	CVE-2007-0008
NVD-ID(s):	CVE-2007-0008
US-CERT Technical Alerts:
Severity Metric:	12.72
Document Revision:	59

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Produced 2007 by US-CERT, a government organization
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