CVE-2021-33766 Exchange ProxyToken Exploitation

Detects the exploitation of Microsoft Exchange ProxyToken vulnerability as described in CVE-2021-33766

Detection logic

selection_1

cs-method: POST
cs-uri-query|contains|all:
  - /ecp/
  - /RulesEditor/InboxRules.svc/NewObject
sc-status: 500

selection_2

cs-uri-query|contains|all:
  - SecurityToken=
  - /ecp/
sc-status: 500

Condition

1 of selection_*

Raw YAML

title: CVE-2021-33766 Exchange ProxyToken Exploitation
id: 56973b50-3382-4b56-bdf5-f51a3183797a
status: test
description: Detects the exploitation of Microsoft Exchange ProxyToken vulnerability as described in CVE-2021-33766
references:
    - https://www.zerodayinitiative.com/blog/2021/8/30/proxytoken-an-authentication-bypass-in-microsoft-exchange-server
author: Florian Roth (Nextron Systems), Max Altgelt (Nextron Systems), Christian Burkard (Nextron Systems)
date: 2021-08-30
modified: 2023-01-02
tags:
    - attack.initial-access
    - attack.t1190
    - cve.2021-33766
    - detection.emerging-threats
logsource:
    category: webserver
detection:
    selection_1:
        cs-method: 'POST'
        cs-uri-query|contains|all:
            - '/ecp/'
            - '/RulesEditor/InboxRules.svc/NewObject'
        sc-status: 500
    selection_2:
        cs-uri-query|contains|all:
            - 'SecurityToken='
            - '/ecp/'
        sc-status: 500
    condition: 1 of selection_*
falsepositives:
    - Unknown
level: critical