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From: Ory Segal (ORY.SEGALSANCTUMINC.COM)
Date: Sun May 19 2002 - 03:00:57 CDT
========================>> Security Advisory <<========================
Multiple vendors web server source code disclosure
(8.3 name format vulnerability - Take II)
=> Author: Ory Segal & Amit Klein - Sanctum inc. http://www.sanctuminc.com
=> Release date: 19/5/2002 (vendor was notified on 9/5/2002)
=> Vendor: General
The following servers where found to be vulnerable:
- Deerfield Website Pro 184.108.40.206 installed on
Microsoft Win2K (SP2).
- Other web servers were found to be vulnerable to this problem,
but we did not yet verify the vulnerability to our full satisfaction.
=> Severity: Medium/High
=> CVE candidate: Not assigned yet.
=> Summary: Several web servers that support requests of files in their 8.3
format name can be tricked (under certain configurations) to present an
server side script, whose file name is at least 3 characters long and whose
extension is at least 4 characters long (e.g. foo.jhtml)
=> Description: On Windows platforms, each "long file name" (file name which
not in DOS 8.3 format) has a "short file name" (in DOS 8.3 format) alternate
name. For example, "longfilename.txt" (which is not in DOS 8.3 format) has
alternate file name "longfi~1.txt", and "name.jumbo" has an alternate file
"name~1.jum". The short file name is basically formed by taking the name
the file name (all characters up to the extension), trimming it to 6
if necessary, and appending "~1" to it, and then trimming the extension to 3
characters if necessary. If there is already a file with that same
name in the directory, then the number (after the "~") is incremented until
free name is found. This scheme has one exception - if the name part is 1-2
characters long, then a different algorithm is used to produce the name
Web servers typically associate a handler to a resource according to its
extension. And typically when no handler is associated with a particular
extension, a default handler is used which returns the raw file.
Some (vulnerable) web servers, running on Windows platforms, fail to
resources, which are requested in their alternate 8.3 format as such, and
simply try to serve these files in the standard manner. This means that the
handler associated with the extension is invoked, and the file is served
this handler (other, non-vulnerable web servers refuse to serve files in the
alternate 8.3 format). This has a severe security impact in
the following configuration:
- a scripting extension name is 4 or more characters long (e.g. jhtml/jhtm
- The trimmed extension (jht and sht) is not associated with the proper
(usually, not associated with any handler).
- The requested script name (excluding the extension) is longer than 2
characters. For example: hello.jhtml and helloworld.shtml In such case, when
requesting the alternate file name (for the script resource), e.g.
and hellow~1.sht, the vulnerable web server does not identify the resource
as an alternate name for a long file name, and attempts to serve the
the standard way. The server first extracts the extension ("jht" and "sht"),
then associate a handler to it (since no handler is defined for "sht" or
the default handler will be used in both cases), and invoke the handler,
returns the file as-is, without running it. This means that the script
returned to the client, instead of the output of the script
=> Solution: If you are running Deerfield WebSite Pro 220.127.116.11, upgrade to
version 18.104.22.168, which is available at:
1. On NTFS (32-bit), you can disable the creation of the 8.3-
compliant short file name for files with long file names by
enabling (setting to 1) the "NtfsDisable8dot3NameCreation"
registry key (registry path:
em\). However, this step may cause compatibility problems
with 16-bit applications.
2. Associate the 8.3 format of the file extension with the
same handler as the original file extension, e.g. if the
extension in use is .jhtml, you should associate .jht with
the same handler.
=> Note: The existence of this vulnerability in the aforementioned web
was discovered by AppScan v3.0 - while running one of its "unknown
vulnerability" tests. This vulnerability does not exist in any other scanner
is not yet registered in BugTraq or any other security resource.
- text/plain attachment: 8.3_Advisory.txt