Novell eDirectory NCP Fragment Denial of Service Vulnerability

iDefense Security Advisory 04.26.07
http://labs.idefense.com/intelligence/vulnerabilities/
Apr 26, 2007

I. BACKGROUND

Novell eDirectory is a cross-platform lightweight directory access
protocol (LDAP) server. In addition to LDAP, eDirectory also implements
NCP over IP. More information can be found on Novell's web site at the
following URL.

http://www.novell.com/products/edirectory/

II. DESCRIPTION

Remote exploitation of a denial of service (DoS) vulnerability in Novell
Inc.'s eDirectory product could allow an attacker to force the running
daemon to cease servicing requests.

The problem specifically exists within the NCP functionality of
eDirectory. Sending a sequence of specially crafted fragmented requests
will cause a DoS condition.

If the input is crafted properly, eDirectory will report to its error
log that a fragment has been received with an invalid length. The error
message includes the contents of the fragments in hexadecimal notation.
However, if the length is negative, eDirectory will try to dump data to
the log indefinitely. This results in a large amount of data being saved
to the log. Once the end of the heap segment is reached, a memory access
violation will occur and the server process will crash.

III. ANALYSIS

Successful exploitation of this vulnerability could allow an attacker to
crash the server process. No credentials are required. Repeated attacks
could allow the attacker to cause excessive disk space usage.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability in version
8.8.1 of Novell Inc.'s eDirectory server with FTF1 applied. The
earliest version tested was 8.8. Earlier versions are suspected to be
vulnerable.

V. WORKAROUND

iDefense is unaware of any effective workaround for this issue.

VI. VENDOR RESPONSE

Novell has addressed this problem within FTF2 for eDirectory 8.8.1. More
information is available in Novell Document ID 3924657 at the following
URL.

http://www.novell.com/support/search.do?cmd=displayKC&docType=kc&externalId=3924657&sliceId=SAL_Public

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2006-4520 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org/), which standardizes names for
security problems.

VIII. DISCLOSURE TIMELINE

08/17/2006  Initial vendor notification
08/18/2006  Initial vendor response
10/21/2006  Second vendor notification
10/23/2006  Vendor response
12/06/2006  Third vendor notification
12/18/2006  Vendor response
03/21/2007  Fourth vendor notification
04/25/2007  Fifth vendor notification
04/25/2007  Vendor advised that the fix was in FTF2
04/26/2007  Coordinated public disclosure

IX. CREDIT

The discoverer of this vulnerability wishes to remain anonymous.

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X. LEGAL NOTICES

Copyright © 2007 iDefense, Inc.

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Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
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