huntrule

Detect suspicious AD SelfService web requests targeting report generation and API endpoints

Flags web requests with URL query strings targeting known ADSelfService exploitation paths for CVE-2021-40539.

FreeReviewedSigma · High · v5
Category
webserver
Author
Tobias Michalski (Nextron Systems), Max Altgelt (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2021-09-20
Updated
2026-07-31
AnalysisDetection

ATT&CK techniques

Initial Access

  1. Recon

  2. Resource Dev

  3. Initial Access

  4. Execution

  5. Persistence

  6. Priv Esc

  7. Defense Evasion

  8. Cred Access

  9. Discovery

  10. Lateral Movement

  11. Collection

  12. C2

  13. Exfiltration

  14. Impact

What it detects

This rule flags webserver activity where the requested URL query contains specific path fragments associated with AD SelfService exploitation attempts. Attackers may use these crafted requests to reach vulnerable report generation and servlet/rest API functionality. The detection relies on webserver telemetry capturing the full request URI query string (cs-uri-query) and matches the presence of the listed endpoint patterns.

Reporting behind it

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Detect suspicious AD SelfService web requests targeting report generation and API endpoints
Pivot detection · T1190 · 9 related

Changelog

v5
  1. v5
    Candidate ingested via manual entry.2026-07-31
  2. v4
    Candidate ingested via manual entry.2026-07-31
  3. v3
    Candidate ingested via manual entry.2026-07-31
  4. v2
    Candidate ingested via manual entry.2026-07-31
  5. v1
    No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.