Fluentd TD-agent 4.0.1 Insecure Folder Permission

Fluentd TD-agent plugin version 4.0.1 suffers from an insecure folder permission vulnerability.

MD5 | 69596b2257ba4a29ed887d023e22351f

# Exploit Title: Fluentd TD-agent plugin 4.0.1 - Insecure Folder Permission
# Date: 21.12.2020
# Exploit Author: Adrian Bondocea
# Vendor Homepage: https://www.fluentd.org/
# Software Link: https://td-agent-package-browser.herokuapp.com/4/windows
# Version: <v4.0.1
# Tested on: Windows 10 x64
# CVE : CVE-2020-28169
# External URL: https://github.com/zubrahzz/FluentD-TD-agent-Exploit-CVE-2020-28169

The td-agent-builder plugin before 2020-12-18 for Fluentd allows attackers to gain privileges because the bin directory is writable by a user account, but a file in bin is executed as NT AUTHORITY\SYSTEM.

Vulnerable Path: ( Authenticated Users have permission to write within the location )
PS C:\opt\td-agent\bin> icacls C:\opt\td-agent\bin
C:\opt\td-agent\bin BUILTIN\Administrators:(I)(OI)(CI)(F)
NT AUTHORITY\Authenticated Users:(I)(M)
NT AUTHORITY\Authenticated Users:(I)(OI)(CI)(IO)(M)

Successfully processed 1 files; Failed processing 0 files

Vulnerable service:
PS C:\opt\td-agent\bin> get-service fluentdwinsvc

Status Name DisplayName
------ ---- -----------
Running fluentdwinsvc Fluentd Windows Service

Service Path:
"C:/opt/td-agent/bin/ruby.exe" -C t"C:/opt/td-agent/lib/ruby/gems/2.7.0/gems/fluentd-1.11.2/lib/fluent/command/.."
winsvc.rb --service-name fluentdwinsvc

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