TippingPoint Zero Day Initiative

Novell Netware RPC XNFS xdrDecodeString Remote Code Execution Vulnerability

ZDI-11-090: February 18th, 2011


CVSS Score

Affected Vendors

Affected Products

TippingPoint™ IPS Customer Protection

TippingPoint IPS customers are protected against this vulnerability by Digital Vaccine protection filter ID 10874. For further product information on the TippingPoint IPS:

Vulnerability Details

This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Novell Netware. Authentication is not required to exploit this vulnerability.

The flaw exists within the XNFS.NLM component which listens by default on UDP port 1234. When handling the an NFS RPC request the xdrDecodeString function uses a user supplied length value to null terminate a string. This value can be signed allowing the NULL byte to be written at an arbitrary address. A remote attacker can exploit this vulnerability to execute arbitrary code under the context of the system.

Vendor Response

Novell has issued an update to correct this vulnerability. More details can be found at:

Disclosure Timeline

    2010-08-25 - Vulnerability reported to vendor
    2011-02-18 - Coordinated public release of advisory


This vulnerability was discovered by:
    Francis Provencher for Protek Researchh Lab's