IBM Tivoli Provisioning Manager for OS Deployment TFTP Blocksize DoS
Vulnerability

iDefense Security Advisory 07.17.07
http://labs.idefense.com/intelligence/vulnerabilities/
Jul 17, 2007

I. BACKGROUND

IBM Corp.'s Tivoli Provisioning Manager for OS Deployment is a network
boot server that facilitates central management of networked
workstations. It implements Preboot Execution Environment (PXE), a
Web-based administration service, DHCP, TFTP, and several additional
protocols. More information can be found at the following URL.

http://www-306.ibm.com/software/tivoli/products/prov-mgr-os-deploy/

II. DESCRIPTION

Remote exploitation of a denial of service vulnerability within version
5.1.0.2 of IBM Corp.'s Tivoli Provisioning Manager for OS Deployment
allows attackers to deny service to all product functionality.

This vulnerability specifically exists in the TFTP protocol
implementation. When processing a read request (RRQ), an integer
division by zero error can be triggered by supplying an invalid
"blksize" argument. This exception is not handled and will result in
the rembo.exe service terminating.

III. ANALYSIS

Exploitation allows an attacker to cause the service to terminate
unexpectedly due to an exception that occurs when dividing by zero.

No authentication is required to access the vulnerable code. The
attacker need only be able to send a specially crafted request to the
TFTP port (UDP port 69) of the vulnerable machine.

This will deny service to all functionality provided by this service.
This includes DHCP, TFTP, PXE, HTTP, HTTPS, as well as several other
services.

IV. DETECTION

iDefense has confirmed the existence of this vulnerability in version
5.1.0.2 of IBM Corp.'s Tivoli Provisioning Manager for OS Deployment.
Version 5.1.0.116 was tested and found not to be vulnerable.

V. WORKAROUND

Employing firewalls to limit access to the affected service will
mitigate exposure to this vulnerability.

VI. VENDOR RESPONSE

The IBM Tivoli team has addressed this vulnerability within Tivoli
Provisioning Manager for OS Deployment 5.1 Fix Pack 3. More information
is available from IBM Document swg24016347 at the following URL.

http://www-1.ibm.com/support/docview.wss?uid=swg24016347

VII. CVE INFORMATION

The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2007-3268 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

06/19/2007  Initial vendor notification
06/19/2007  Initial vendor response
07/17/2007  Coordinated public disclosure

IX. CREDIT

This vulnerability was reported to iDefense by Manuel Santamarina
Suarez.

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X. LEGAL NOTICES

Copyright © 2007 iDefense, Inc.

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