Updated Apache httpd packages that correct security issues and resolve bugs
are now available for CentOS Linux 3 and 4.
This update has been rated as having moderate security impact by the Red
Hat Security Response Team.
The Apache HTTP Server is a popular Web server available for free.
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
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.
On CentOS Linux 3 and 4 systems, due to an unrelated issue in
the handling of malformed Expect headers, the page produced by the
cross-site scripting attack will only be returned after a timeout expires
(2-5 minutes by default) if not first canceled by the user.
Users of httpd should update to these erratum packages, which contain a
backported patch to correct these issues.