Tomcat Vulnerability Allows Unintended Directory Listings

By ServerWatch Staff (Send Email)
Posted Jan 30, 2003


Apache's Tomcat JSP/Servlet implementation contains a vulnerability that allows remote users to retrieve directory listings. Details and a link to the update correcting the vulnerability are included in this vulnerability announcement from Jouko Pynnonen: Apache's Tomcat JSP/Servlet implementation contains a vulnerability that allows remote users to retrieve directory listings. Details and a link to the update correcting the vulnerability are available.

Date: Thu, 30 Jan 2003 14:53:23 +0200 (EET)
From: Jouko Pynnonen 
Subject: Apache Jakarta Tomcat 3 URL parsing vulnerability

OVERVIEW

Tomcat is a JSP/Servlet implementation developed at the Apache Software Foundation. Tomcat versions 3.3.1 and earlier contain some security vulnerabilities which allow a remote user to retrieve listings of directories despite index.html or index.jsp files. It is also possible to retrieve contents of files and directories that shouldn't be visible to outside. The vulnerability also allows retrieving the source of JSP files.

DETAILS

Certain kinds of HTTP requests containing binary null or backslash characters are parsed incorrectly by Tomcat's built-in web server. The following GET request causes Tomcat to output the directory listing of the web root under default installation:

GET /<null byte>.jsp HTTP/1.0

The following UNIX command can be issued to test the vulnerability:

$ perl -e 'print "GET /\x00.jsp HTTP/1.0\r\n\r\n";' | nc my.server 8080

If your server is vulnerable, the command will output a HTTP header and the directory listing even if there's an index file present. Furthermore, a backslash can be used in the following way to get information from otherwise inaccessible directories:

$ perl -e 'print "GET
/admin/WEB-INF\\classes/ContextAdmin.java\x00.jsp HTTP/1.0\r\n\r\n";'|nc my.server 8080

This will output the contents of ContextAdmin.java.

The servlet engine interprets the directory listing and any file retrieved in this way as a JSP page, which might be exploited to run arbitrary Java code under some imaginable scenarios. If the attacker can create a file whose name contains JSP tags somewhere under the web root, the code would be run when the directory listing is fetched in the way described above. Similarly Java code embedded in *.html or any other file can be compiled and run by an attacker.

In the same way a remote user may force a *.jsp file to be interpreted as plain HTML, ie. retrieve the source of JSP files:

$ perl -e 'print "GET /examples/jsp/cal/cal1.jsp\x00.html HTTP/1.0\r\n\r\n";'|nc my.server 8080

This would output the source of the example JSP file.

SOLUTION

The vendor was informed on January 10, 2003. A new version of Tomcat addressing this problem has been released. The fixed version 3.3.1a and additional information is available at

http://jakarta.apache.org/builds/jakarta-tomcat/release/v3.3.1a/

According to the vendor, the problem only affects Tomcat used with JDK 1.3.1 or earlier.

CREDITS

The vulnerability was discovered by Jouko Pynnönen of Online Solutions Ltd, Finland.

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