Title: Unchecked Buffer in ASP.NET Worker Process (Q322289)
Date: 06 June 2002
Software: .NET Framework
Impact: Denial of service, potentially run code of attacker's
choice
Max Risk: Moderate
Bulletin: MS02-026

Microsoft encourages customers to review the Security Bulletin at:
http://www.microsoft.com/technet/security/bulletin/MS02-026.asp.

Issue:

ASP.NET is a collection of technologies that help developers to
build web-based applications. Web-based applications, including
those built using ASP.NET, rely on HTTP to provide connectivity.
One characteristic of HTTP as a protocol is that it is stateless,
meaning that each page request from a user to a site is reckoned
an independent request. To compensate for this, ASP.NET provides
for session state management through a variety of modes.

One of these modes is StateServer mode. This mode stores session
state information in a separate, running process. That process
can run on the same machine or a different machine from the
ASP.NET application. There is an unchecked buffer in one of the
routines that handles the processing of cookies in StateServer
mode. A security vulnerability results because it is possible
for an attacker to seek to exploit it by mounting a buffer
overrun attack. A successful attack could cause the ASP.NET
application to restart. As a result, all current users of
the web-based application would see their current session
restart and their current session information would be lost.

The StateServer mode is not the default mode for session
state management in ASP.NET. ASP.NET applications using
StateServer mode that do not use cookies are not vulnerable.

Mitigating Factors:

• StateServer mode is not the default mode for session state
  management in ASP.NET. That ASP.NET application would have
  to be specifically configured to use this mode.
• Even if an application was configured to use StateServer
  mode, it would only be at risk if it also used cookies.

Risk Rating:

• Internet systems: Moderate
• Intranet systems: Moderate
• Client systems: None

Patch Availability:

• A patch is available to fix this vulnerability. Please read the
  Security Bulletin at
  http://www.microsoft.com/technet/security/bulletin/ms02-026.asp
  for information on obtaining this patch.

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