huntrule

Detect CVE-2023-4966 Citrix ADC Sensitive Info Disclosure Attempts in Webserver Logs via Long Host Header

Alerts on GET requests to the OpenID configuration endpoint with an unusually long Host header, indicative of CVE-2023-4966 probing.

FreeReviewedSigma · High · v5
Category
webserver
Author
Nasreddine Bencherchali (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2023-11-28
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 HTTP GET requests to the OpenID configuration path used in OAuth/OIDC flows while the host header value matches a very long pattern (150+ characters). Attackers may leverage this behavior to probe or attempt exploitation of the Citrix ADC and NetScaler Gateway sensitive information disclosure issue. It relies on webserver telemetry fields for request method, URI stem, and host header length/pattern matching.

Reporting behind it

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Detect CVE-2023-4966 Citrix ADC Sensitive Info Disclosure Attempts in Webserver Logs via Long Host Header
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.