Vulnerability Note VU#402580

Jetty HTTP server directory traversal vulnerability

Overview

A vulnerability in the Jetty HTTP server could allow a remote attacker to gain access to files outside of the normal document tree.

I. Description

Jetty provides an HTTP server, HTTP client, and javax.servlet container. An error in the way canonical paths are interpreted in the HTTP server's URI handler results in a directory traversal vulnerability. This vulnerability affects all versions of Jetty up to and including jetty 6.1.16 and 7.0.0.M2. In order for a system to be vulnerable, it must either be using the DefaultServlet with support for aliases explicitly enabled or the ResourceHandler class to serve static content. The vendor reports that systems running Jetty on Unix-like operating systems must also contain a directory name ending a '?' character in the web application or document root in order to be vulnerable.

II. Impact

A remote attacker can access files outside of the web application or document root by supplying a crafted URL to an vulnerable system.

III. Solution

Upgrade or apply a patch from the vendor

Jetty version 6.1.17 has been published to address this vulnerability. Users are encouraged to upgrade to this version.

The vendor has described the following workarounds for users who are unable to update their software:

If you are not using the ResourceHandler, then you should confirm that your jetty instance is running with the Default servlet "aliases" initParam set to "false". You will find this setting in either your application's web.xml or the etc/webdefault.xml. If it is not set, then it takes the default, safe, value of "false". You should also check that the org.mortbay.util.FileResource.checkAliases system property is either not set, or set to true. If you are using the ResourceHandler, then you can secure your system against this vulnerability by compiling the source at the bottom of this message against the version of Jetty that you are using. Use an instance of this class instead of the ResourceHandler

package org.mortbay.jetty.cert;

import java.net.MalformedURLException;

import org.mortbay.jetty.handler.ResourceHandler;

import org.mortbay.resource.Resource;

import org.mortbay.util.StringUtil;

import org.mortbay.util.URIUtil;

public class TempFixResourceHandler extends ResourceHandler

{

public Resource getResource(String path) throws MalformedURLException

{

if (path!=null && path.indexOf('?')>=0)

{

path=URIUtil.decodePath(URIUtil.canonicalPath(StringUtil.replace(path,"?","%3F")));

if (path==null)

return null;

}

return super.getResource(path);

}

Systems Affected

Vendor	Status	Date Updated
Mort Bay	Vulnerable		2009-05-01

References

http://docs.codehaus.org/display/JETTY/Jetty+Security
http://jira.codehaus.org/browse/JETTY-1004

Credit

Thanks to Greg Wilkins of Mort Bay Consulting for reporting this vulnerability.

This document was written by Chad R Dougherty.

Other Information

Date Public	04/29/2009
Date First Published	05/01/2009 03:39:26 PM
Date Last Updated	05/01/2009
CERT Advisory
CVE Name
Metric	6.60
Document Revision	9

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