Vulnerability Note VU#916785

Buffer overflow in Snort RPC preprocessor

Original Release date: 03 Mar 2003 | Last revised: 19 May 2003


There is a buffer overflow vulnerability in the RPC preprocessing feature of Snort versions 1.8 through 1.9.0 and 2.0 beta.


Martin Roesch, the primary Snort developer, described the vulnerability by saying:

    When the RPC decoder normalizes fragmented RPC records, it incorrectly checks the lengths of what is being normalized against the current packet size, leading to an overflow condition. The RPC preprocessor is enabled by default.

The ISS X-Force team has published an advisory with additional information on this issue:

Information about this vulnerability can also be found on the Snort web site at:


A remote attacker can execute arbitrary code as the user running the Snort process, usually root. The attacker does not need to send packets directly to the Snort sensor. It is sufficient to send packets to any of the hosts on the network monitored by Snort.


Upgrade to Snort version 1.9.1

Disable the rpc_decode preprocessor

    You can prevent exploitation of this vulnerability by commenting out the rpc_decode preprocessor in the "snort.conf" configuration file. Note that this change may affect your ability to correctly process RPC record fragments.

Block outbound packets from Snort IDS systems
    You may be able limit an attacker's capabilities if the system is compromised by blocking all outbound traffic from the Snort sensor. While this workaround will not prevent exploitation of the vulnerability, it may make it more difficult for the attacker to create a useful exploit.

Systems Affected (Learn More)

VendorStatusDate NotifiedDate Updated
ConectivaAffected16 Apr 200317 Apr 2003
DebianAffected16 Apr 200319 May 2003
Gentoo LinuxAffected06 Mar 200319 May 2003
Guardian Digital Inc. Affected16 Apr 200317 Apr 2003
MandrakeSoftAffected16 Apr 200317 Apr 2003
SmoothWallAffected07 Mar 200321 Apr 2003
SnortAffected28 Feb 200317 Apr 2003
Apple Computer Inc.Not Affected16 Apr 200317 Apr 2003
FujitsuNot Affected16 Apr 200319 May 2003
Ingrian NetworksNot Affected16 Apr 200317 Apr 2003
NetBSDNot Affected16 Apr 200317 Apr 2003
Red Hat Inc.Not Affected16 Apr 200317 Apr 2003
SGINot Affected16 Apr 200317 Apr 2003
BSDIUnknown16 Apr 200317 Apr 2003
Cray Inc.Unknown16 Apr 200317 Apr 2003
If you are a vendor and your product is affected, let us know.View More »

CVSS Metrics (Learn More)

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



Thanks to ISS X-Force for discovering this vulnerability, and to Martin Roesch for his assistance in developing this document.

This document was written by Cory F. Cohen.

Other Information

  • CVE IDs: CAN-2003-0033
  • CERT Advisory: CA-2003-13
  • Date Public: 03 Mar 2003
  • Date First Published: 03 Mar 2003
  • Date Last Updated: 19 May 2003
  • Severity Metric: 6.41
  • Document Revision: 21


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