Sourcefire Snort Remote Buffer Overflow

Notification Type: IBM Internet Security Systems Protection Advisory
Notification Date: Feb 19, 2007
Notification Version: 1.0
Name: Sourcefire Snort Remote Buffer Overflow
Public disclosure/
In the wild date:
Feb 19, 2007
Description: Snort IDS and Sourcefire Intrusion Sensor IDS/IPS are vulnerable to a stack-based buffer overflow, which can result in remote code execution.
Credit: This vulnerability was discovered and researched by Neel Mehta of the IBM Internet Security Systems X-Force.


ISS Coverage

Product Content Version
Network Sensor 7.0
Proventia A
Proventia IPS (G/GX) prior to Firmware Version 1.2
Server Sensor 7.0
Proventia IPS (G/GX) Firmware Version 1.2 or
Proventia Multifunction Appliance
Proventia Server (Linux)
Proventia Server (Windows) 1.0.914.1960
Proventia Desktop 8.0.x.1960
RealSecure Desktop 7.0 (AM SP 6.73 or 7.73) EQB
BlackICE PC Protection 3.6 CQB
Propagation Techniques ISS Protection Available
network exploit  SMB_WriteAndX_Frag_Bo Feb 15, 2007 

Detailed Description

Business Impact: Compromise of machines using affected versions of Snort or Sourcefire may lead to exposure of confidential information, loss of productivity, and further compromise.  Successful exploitation of this vulnerability results in remote code execution with the privilege level of Snort, usually root or SYSTEM. Exploitation of this vulnerability does not require user interaction. 
CVSS: Base Score: 10 
  Access Vector: Remote 
Access Complexity: Low 
Authentication: Not Required
Confidentiality Impact: Complete 
Integrity Impact: Complete 
Availability Impact: Complete 
Impact Bias: Normal 
Adjusted Temporal Score: 7.4 
  Exploitability: Unproven 
Remediation Level: Official Fix 
Report Confidence: Confirmed 
Affected Products:
  • Snort 2.6.1,, and
  • Snort 2.7.0 beta 1
  • Sourcefire Intrusion Sensors versions 4.1.x, 4.5.x, and 4.6.x with SEUs prior to SEU 64
  • Sourcefire Intrusion Sensor Software for Crossbeam versions 4.1.x, 4.5.x and 4.6.x with SEUs prior to SEU 64
Technical Description: Snort is vulnerable to a stack-based buffer overflow as a result of DCE/RPC reassembly. This vulnerability is in a dynamic-preprocessor enabled in the default configuration, and the configuration for this preprocessor allows for auto-recognition of SMB traffic to perform reassembly on. No checks are performed to see if the traffic is part of a valid TCP session, and multiple Write AndX requests can be chained in the same TCP segment. As a result, an attacker can exploit this overflow with a single TCP PDU sent across a network monitored by Snort or Sourcefire. 

The affected Snort versions use a DCE/RPC + SMB preprocessor for reassembling DCE/RPC messages fragmented across multiple higher-level protocol messages.  The SMB preprocessor in particular exists primarily to reassemble DCE/RPC IPC transactions conducted via an NT named pipe over SMB.

Snort users who cannot upgrade immediately are advised to disable the DCE/RPC preprocessor by removing the DCE/RPC preprocessor directives from snort.conf and restarting Snort. However, be advised that disabling the DCE/RPC preprocessor reduces detection capabilities for attacks in DCE/RPC traffic. After upgrading, customers should re-enable the DCE/RPC preprocessor. 


Sourcefire: tbd

Revision History

1.0 Initial release.

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