Public Vulnerability Reports

Novell eDirectory NCP Fragment Denial of Service Vulnerability



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.


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.


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.


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.


iDefense is unaware of any effective workaround for this issue.


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.


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 (, which standardizes names for security problems.


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


The discoverer of this vulnerability wishes to remain anonymous.

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Copyright © 2007 Verisign, Inc.

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