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Summary

Improves excluded params in ParametersInterceptor and CookieInterceptor to avoid ClassLoader manipulation

Who should read this

All Struts 2 developers and users

Impact of vulnerability

ClassLoader manipulation

Maximum security rating

Important

Recommendation

Developers should immediately upgrade to Struts 2.3.16.2

Affected Software

Struts 2.0.0 - Struts 2.3.16.1

Reporter

Taki Uchiyama (JPCERT/CC), Takeshi Terada (Mitsui Bussan Secure Directions, Inc.), Takayoshi Isayama (Mitsui Bussan Secure Directions, Inc.), Yoshiyuki Karezaki, BAKA/ty, Shine (1983059165 at qq.com), NSFOCUS Security Team

CVE Identifier

CVE-2014-0112 - Incomplete fix for ClassLoader manipulation via ParametersInterceptor

CVE-2014-0113 - ClassLoader manipulation via CookieInterceptor when configured to accept all cookies

Problem

The default upload mechanism in Apache Struts 2 is based on Commons FileUpload version 1.3 which is vulnerable and allows DoS attacks. Additional ParametersInterceptor allows access to 'class' parameter which is directly mapped to getClass() method and allows ClassLoader manipulation.

Solution

In Struts 2.3.16.1, Commons FileUpload was updated to version 1.3.1 and "class" was added to excludeParams in struts-default.xml configuration of ParametersInterceptor.

Backward compatibility

No backward compatibility problems are expected.

Workaround

If you cannot upgrade to version 2.3.16.1 which is strongly advised, you can apply below workarounds:

Upgrade commons-fileupload

The fixed commons-fileupload library is a drop-in replacement for the vulnerable version. Deployed applications can be hardened by replacing the commons-fileupload jar file in WEB-INF/lib with the updated jar. For Maven
based Struts 2 projects, the following dependency needs to be added:

<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.3.1</version>
</dependency>

Exclude 'class' parameter

Simple add '^class\.*' to the list of excludeParams as below

<interceptor-ref name="params">
  <param name="excludeParams">^class\..*,^dojo\..*,^struts\..*,^session\..*,^request\..*,^application\..*,^servlet(Request|Response)\..*,^parameters\..*,^action:.*,^method:.*</param>
</interceptor-ref>
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