Sigma rule: Exchange Exploitation CVE-2021-28480

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-e7533395e366, updated 2023-01-02T00:00:00.000Z.

Rule

Title
Exchange Exploitation CVE-2021-28480
Status
test
Level
critical
Author
Florian Roth (Nextron Systems)
Date
2021-05-14
Modified
2023-01-02
File
rules-emerging-threats/2021/Exploits/CVE-2021-28480/web_cve_2021_28480_exchange_exploit.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects successful exploitation of Exchange vulnerability as reported in CVE-2021-28480

Log source

category
webserver

Detection

selection:
    cs-uri-query|contains: '/owa/calendar/a'
    cs-method: 'POST'
filter_main_status:
    sc-status: 503
condition: selection and not 1 of filter_*

False positives (as the rule lists them)

  • Unknown

Tags

  • attack.initial-access
  • attack.t1190
  • cve.2021-28480
  • 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-2021-28480/web_cve_2021_28480_exchange_exploit.yml

Sources and licences

  • SigmaHQ

    "Exchange Exploitation CVE-2021-28480" by Florian Roth (Nextron Systems) (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules-emerging-threats/2021/Exploits/CVE-2021-28480/web_cve_2021_28480_exchange_exploit.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: Exchange Exploitation CVE-2021-28480",
entity page, dataset version ref-e7533395e366, updated 2023-01-02T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/a2a9d722-0acb-4096-bccc-daaf91a5037b (accessed 2026-11-03).
Underlying source: SigmaHQ rule a2a9d722-0acb-4096-bccc-daaf91a5037b, 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.