Informix Long Username Buffer Overflow Vulnerability

NGSSoftware Insight Security Research Advisory

Name: Informix Long Username Buffer Overflow Vulnerability
Systems Affected: Informix 9.40.xC6 and earlier, 10.00.xC2 and earlier
Severity: Critical
Vendor URL:
Author: David Litchfield [ davidl@xxxxxxxxxxxxxxx ]
Date of Public Advisory: 2nd August 2006
Advisory number: #NISR02082006A
Advisory URL:

Informix Dynamic Server is a database developed by IBM. During a security assessment of the database it was found to be vulnerable to a stack based buffer overflow in the authentication procedure.

When an Informix server logs on a user it copies the username to a 260 byte stack based buffer without first verifying its length. An attacker can exploit this by overflowing this buffer to overwrite the saved return address on the stack and thus redirect the process' path of execution to a location of their choosing.

Whilst the IBM advisory indicates that only Informix running on Windows is vulnerable to this NGS we're able to determine that Informix running on Linux is also vulnerable.

Fix Information
IBM was alerted to this flaw on the 6th January 2005; a fix has now been made available. IBM's advisory on the matter can be found here:

NGSSQuirreL for Informix, an advanced vulnerability assessment scanner designed specifically for Informix, can be used to accurately determine whether your servers are vulnerable to this flaw. More information about NGSSQuirreL for Informix can be found here

About NGSSoftware

NGSSoftware develops vulnerability assessment and compliancy tools for database servers including Oracle, Microsoft SQL Server, DB2, Sybase and Informix. Headquartered in the United Kingdom NGS has offices in London, St. Andrews (UK), Sydney, Brisbane, and Perth (Australia) and Texas in the United States; NGSConsulting provide services to some of the largest and most demanding organizations around the globe.

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