The System.Web class in the XSP for ASP.NET server 1.1 through 2.0 in Mono does not properly verify local pathnames, which allows remote attackers to (1) read source code by appending a space (%20) to a URI, and (2) read credentials via a request for Web.Config%20.

Researcher

José Ramón Palanco: jpalanco@gmail.com

Details

Time Line

Nov 29, 2006: Discovered security issue by Jose Ramon Palanco
Nov 30, 2006: Reported to Mono Project
Dec 1, 2006: Patch in subversion rev 68776
Dec 5, 2006: Mono is testing the patch and building packages for the fix
Dec 19, 2006: Published advisory

Vulnerability

Source Code Disclosure and Configuration Disclosure

Attackers use source code disclosure attacks to try to obtain the source code of server-side applications. The basic role of Web servers is to serve files as requested by clients. Files can be static, such as image and HTML files, or dynamic, such as ASPX, ASHX, ASCX, ASAX, webservices like ASMX files and any language supported by Mono like: C#, boo, nemerle, vb files: .cs, .boo, vb, .n, … When the browser requests a dynamic file, the Web server first executes the file and then returns the result to the browser. Hence, dynamic files are actually code executed on the Web server.

Using a source code disclosure attack, an attacker can retrieve the source code of server-side file. Obtaining the source code of server-side files grants the attacker deeper knowledge of the logic behind the Web application, how the application handles requests and their parameters, the structure of the database, vulnerabilities in the code and source code comments. Having the source code, and possibly a duplicate application to test on, helps the attacker to prepare an attack on the application.

An attacker can cause source code disclosure using adding %20 (space char) after the uri, for example http://www.server.com/app/Default.aspx%20

Update: is also possible retrieve Web.Config file. This file contains sensible information like credentials.

Products and Versions

Type	Vendor	Product	Version
Application	Mono	XSP	1.1
Application	Mono	XSP	1.2.1
Application	Mono	XSP	2.0

CPE v2.3

cpe:2.3:a:mono:xsp:1.1:::::::*
cpe:2.3:a:mono:xsp:1.2.1:::::::*
cpe:2.3:a:mono:xsp:2.0:::::::*

OVAL Definitions

Title	Definition id	Family
mono-web ASP.net sourcecode disclosure	oval:org.mitre.oval:def:2092	unix

CVSS Scores & Vulnerability Types

Name	Value
CVSS Score	5.0
Confidentiality Impact	Partial (There is considerable informational disclosure.)
Integrity Impact	None (There is no impact to the integrity of the system)
Availability Impact	None (There is no impact to the availability of the system.)
Access Complexity	Low (Specialized access conditions or extenuating circumstances do not exist. Very little knowledge or skill is required to exploit. )
Authentication	Not required (Authentication is not required to exploit the vulnerability.)
Gained Access	None
Vulnerability Type(s)
CWE ID	CWE id is not defined for this vulnerability

CVE-2006-6104: Mono XSP ASP.NET Server sourcecode disclosure