BremsServer Input Validation Flaw Discloses Files to Remote Users
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SecurityTracker Alert ID: 1008853
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CVE Reference: GENERIC-MAP-NOMATCH
(Links to External Site)
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Date: Jan 26 2004
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Impact: Disclosure of authentication information, Disclosure of system information, Disclosure of user information, Execution of arbitrary code via network, Modification of user information
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Exploit Included: Yes
Vendor Confirmed: Yes
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Version(s): 1.2.4
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Description: An input validation vulnerability was reported in BremsServer. A remote user can view files on the system. A remote user can also conduct cross-site scripting attacks.
Donato Ferrante reported that a remote user can supply a specially crafted URL containing '../' directory traversal characters to
view arbitrary files on the target system with the privileges of the web service.
A demonstration exploit URL is provided:
http://[target]/../PATH/windows/system.in
i
It is also reported that the web server does not filter HTML code from user-supplied input before displaying messages that
contain the input. A remote user can create a specially crafted URL that, when loaded by a target user, will cause arbitrary scripting
code to be executed by the target user's browser. The code will originate from the site running the BremsServer software and will
run in the security context of that site. As a result, the code will be able to access the target user's cookies (including authentication
cookies), if any, associated with the site, access data recently submitted by the target user via web form to the site, or take
actions on the site acting as the target user.
A demonstration exploit URL is provided:
http://[target]/<script>alert("Test")</script>
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Impact: A remote user can view files on the system located outside of the web document directory. Files can be viewed with the privileges
of the web service.
A remote user can access the target user's cookies (including authentication cookies), if any, associated
with the site running the BremsServer software, access data recently submitted by the target user via web form to the site, or take
actions on the site acting as the target user.
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Solution: No solution was available at the time of this entry. The report indicates that the vendor will fix the flaws in the next version.
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Vendor URL: www.herberlin.de/bremsserver.php (Links to External Site)
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Cause: Access control error, Input validation error
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Underlying OS: Linux (Any), UNIX (Any), Windows (Any)
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Reported By: "Donato Ferrante" <fdonato@autistici.org>
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Message History:
None.
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Source Message Contents
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Date: Mon, 26 Jan 2004 14:48:22 +0100
From: "Donato Ferrante" <fdonato@autistici.org>
Subject: Directory traversal and XSS in BremsServer 1.2.4
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Donato Ferrante
Application: BremsServer
http://www.herberlin.de/
Version: 1.2.4
Bugs: directory traversal and cross site scripting
Author: Donato Ferrante
e-mail: fdonato@autistici.org
web: www.autistici.org/fdonato
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1. Description
2. The bugs
3. The code
4. The fix
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1. Description:
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Vendor's Description:
"Herberlin BremsServer is a small HTTP server you can use to test your
web pages on your local machine."
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2. The bugs:
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[1] directory traversal bug, the program does't make a good check on
the user input string ( /../ ) so an attacker is able to see and
download all the files on the remote system simply using his
browser.
[2] cross site scripting bug, the program doesn't make a full check
on the strings sent by the client, in fact the input strings are
not filtered and they will appear in the returned page.
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3. The code:
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To test the vulnerabilities:
[1]
http://[host]/../PATH/windows/system.ini
[2]
http://[host]/<script>alert("Test")</script>
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4. The fix:
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Bugs will be fixed in the next version of BremsServer. So go on the
BremsServer's official web site: http://www.herberlin.de/
and check for a new version.
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