Public Vulnerability Reports

Mozilla Network Security Services SSLv2 Server Stack Overflow Vulnerability

02.23.07

BACKGROUND

Network Security Services (NSS) is a set of libraries designed to support cross-platform development of security-enabled client and server applications, providing support for, among others, SSL (Secure Socket Layer) protocol version 2 and 3. For more information visit the following URL.

http://www.mozilla.org/projects/security/pki/nss/tools/

DESCRIPTION

Remote exploitation of an input validation error causing an integer underflow in version 3.10 of the Mozilla Foundation's Network Security Services (NSS) may allow an attacker to cause a stack-based buffer overflow and execute arbitrary code on the affected application.

The vulnerability specifically exists in code responsible for handling the client master key. While negotiating an SSLv2 session, a client can specify invalid parameters which causes an integer underflow. The resulting value is used as the amount of memory to copy into a fixed size stack buffer. As a result, a potentially exploitable stack-based buffer overflow condition occurs.

ANALYSIS

Successful exploitation of this vulnerability would allow an attacker to execute arbitrary code in the context of the affected server. No authentication is required to reach the vulnerable code. No user interaction is required.

Since this vulnerability is in library code used by multiple applications, the details of how an attacker would exploit it vary. In all cases, an attacker would need to specify invalid parameters as part of the SSLv2 handshake.

Code execution has been demonstrated to be possible under Windows 2000 with a server utilizing the affected library. Depending on the precise details of the server, this vulnerability may also be exploitable on other platforms.

DETECTION

iDefense has confirmed this vulnerability exists in versions 3.10 and 3.11.3 of the Mozilla Network Security Services. These libraries are used in a variety of products from multiple vendors including Sun Microsystems, Red Hat and Mozilla. Previous versions are also likely to be affected. The names 'libnss3.so' on Linux based systems or 'nss3.dll' on Windows based systems may indicate the library is being used by an application.

WORKAROUND

iDefense is not aware of any effective workaround for this vulnerability. With some servers it may be possible to prevent exposure by disabling SSLv2 support and employing a different protocol. However, this workaround may prevent some clients from being able to access the server.

VENDOR RESPONSE

The Mozilla Foundation has addressed this vulnerability in Mozilla Foundation Security Advisory 2007-06. For more information, view their advisory at the following URL.

http://www.mozilla.org/security/announce/2007/mfsa2007-06.html

CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the name CVE-2007-0009 to this issue. This is a candidate for inclusion in the CVE list (http://cve.mitre.org/), which standardizes names for security problems.

DISCLOSURE TIMELINE

12/18/2006 Initial vendor notification
12/19/2006 Initial vendor response
02/23/2007 Coordinated public disclosure

CREDIT

This vulnerability was reported to iDefense by regenrecht.

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LEGAL NOTICES

Copyright © 2007 Verisign, Inc.

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