Knowledge Base

• 2.0.2
• 2.1.3
• 2.5.3
• 2.5.4
• 2.5.5
• 3.0.0
• 3.0.1

Problem Description

http_protocol.c in (1) IBM HTTP Server 6.0 before 6.0.2.13 and 6.1 before 6.1.0.1, and (2) Apache HTTP Server 1.3 before 1.3.35, 2.0 before 2.0.58, and 2.2 before 2.2.2, does not sanitize the Expect header from an HTTP request when it is reflected back in an error message, which might allow cross-site scripting (XSS) style attacks using web client components that can send arbitrary headers in requests, as demonstrated using a Flash SWF file.

A bug was found in Apache where an invalid Expect header sent to the server was returned to the user in an unescaped error message. This could allow an attacker to perform a cross-site scripting attack if a victim was tricked into connecting to a site and sending a carefully crafted Expect header. (CVE-2006-3918)

While a web browser cannot be forced to send an arbitrary Expect header by a third-party attacker, it was recently discovered that certain versions of the Flash plugin can manipulate request headers. If users running such versions can be persuaded to load a web page with a malicious Flash applet, a cross-site scripting attack against the server may be possible.