Vulnerability Note VU#433596

Ethereal integer underflow when parsing malformed PGM packets with NAK lists

Original Release date: 24 Mar 2004 | Last revised: 25 Mar 2004


Ethereal fails to properly parse Pragmatic General Multicast (PGM) packets containing a crafted negative acknowledgement (NAK) list.


Ethereal is a network traffic analysis package. It includes the ability to decode packets containing PGM data. There is a vulnerability in the way the PGM protocol dissector parses PGM data containing a crafted NAK list.

According to the e-matters Security Advisory:

    "When parsing an PGM packet with a carefully crafted NakList a possible integer underflow can result in a very small stack-overflow. Due to the stacklayout code execution exploitation seems very unlikely."


A remote, unauthenticated attacker could cause Ethereal to crash or possibly execute arbitrary code on the vulnerable system.


Upgrade to version 0.10.3 or later.

Note: Ethereal is considered BETA software at this time.

Disable Dissector

If you are unable to upgrade to version 0.10.3 or later, you can disable the PGM protocol dissector by performing the following actions in Ethereal:

(for Ethereal versions 0.8.x and 0.9.x)

    1) Select Edit->Protocols
    2) Deselect the PGM protocol dissector from the list

(for Ethereal versions 0.10.x)
    1) Select Analyze->Enabled Protocols
    2) Disable the PGM protocol dissector from the list by unchecking its "Status" checkbox

Systems Affected (Learn More)

VendorStatusDate NotifiedDate Updated
EtherealAffected-24 Mar 2004
If you are a vendor and your product is affected, let us know.

CVSS Metrics (Learn More)

Group Score Vector
Base N/A N/A
Temporal N/A N/A
Environmental N/A N/A



Ethereal credits Stefan Esser for reporting this vulnerability.

This document was written by Damon Morda.

Other Information

  • CVE IDs: CAN-2004-0176
  • Date Public: 22 Mar 2004
  • Date First Published: 24 Mar 2004
  • Date Last Updated: 25 Mar 2004
  • Severity Metric: 4.04
  • Document Revision: 21


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