Sigma rule: CVE-2021-33766 Exchange ProxyToken Exploitation

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-338d57ab07b2, updated 2023-01-02T00:00:00.000Z.

Rule

Title
CVE-2021-33766 Exchange ProxyToken Exploitation
Status
test
Level
critical
Author
Florian Roth (Nextron Systems), Max Altgelt (Nextron Systems), Christian Burkard (Nextron Systems)
Date
2021-08-30
Modified
2023-01-02
File
rules-emerging-threats/2021/Exploits/CVE-2021-33766/web_cve_2021_33766_msexchange_proxytoken.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

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

Log source

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_*

False positives (as the rule lists them)

  • Unknown

Tags

  • attack.initial-access
  • attack.t1190
  • cve.2021-33766
  • detection.emerging-threats

CVEs this rule names

MITRE ATT&CK ids this rule names

References

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules-emerging-threats/2021/Exploits/CVE-2021-33766/web_cve_2021_33766_msexchange_proxytoken.yml

Sources and licences

  • SigmaHQ

    "CVE-2021-33766 Exchange ProxyToken Exploitation" by Florian Roth (Nextron Systems), Max Altgelt (Nextron Systems), Christian Burkard (Nextron Systems) (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules-emerging-threats/2021/Exploits/CVE-2021-33766/web_cve_2021_33766_msexchange_proxytoken.yml.
    Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License

    Detection Rule License (DRL) 1.1

Cite this page

Dragons Eye Ransomware Tracker, "Sigma rule: CVE-2021-33766 Exchange ProxyToken Exploitation",
entity page, dataset version ref-338d57ab07b2, updated 2023-01-02T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/56973b50-3382-4b56-bdf5-f51a3183797a (accessed 2026-11-03).
Underlying source: SigmaHQ rule 56973b50-3382-4b56-bdf5-f51a3183797a, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.