Skip to content
attack.paths
Connexion
← RegistryDossier · 6 steps · 5 edges

ProxyShell → SYSTEM on Exchange → DA

Pre-auth ProxyShell chain (path confusion + EWS email-to-PowerShell + arbitrary file write) deploys a webshell as SYSTEM. Same post-exploitation as ProxyLogon.

Filed by AD Knowledge Base
§ Kill-chainDrag · zoom · scroll

§ Context

Assumed environment: on-prem Exchange unpatched for CVE-2021-34473 / -34523 / -31207. Autodiscover reachable. Reaches internal AD via the Exchange machine account's privileges.

§ Steps

  1. 01
    Pivot to AD via Exchange privilegesPersistence
    AD-ADMINSDHOLDER— AdminSDHolder Abuse
  2. 02
    DCSyncCredential Access
    T1003.006— DCSync
  3. 03
    Confirm Exchange versionReconnaissance
    W-RECON-FINGERPRINT— Tech Stack Fingerprinting
  4. 04
    Webshell as SYSTEMPersistence
    W-WEBSHELL— Webshell Deployment
  5. 05
    Dump LSASS / harvest tokensCredential Access
    W-LSASS-PROCDUMP— LSASS via procdump / comsvcs.dll
  6. 06
    Trigger ProxyShell chainInitial Access
    EX-PROXYSHELL— ProxyShell (CVE-2021-34473/-34523/-31207)

§ References

§ Frequently asked

What is the "ProxyShell → SYSTEM on Exchange → DA" attack path?
Pre-auth ProxyShell chain (path confusion + EWS email-to-PowerShell + arbitrary file write) deploys a webshell as SYSTEM. Same post-exploitation as ProxyLogon. It chains 6 steps drawn from real-world offensive-security techniques.
What starting position does this attack require?
The first step is Pivot to AD via Exchange privileges (AD-ADMINSDHOLDER) — a persistence primitive. Assumed environment: on-prem Exchange unpatched for CVE-2021-34473 / -34523 / -31207.
What is the final impact of this kill-chain?
The final step lands on Trigger ProxyShell chain (EX-PROXYSHELL), which falls under Initial Access. From here, an operator typically pivots into post-exploitation or maintains persistence.
How can defenders detect or prevent this attack?
Detection and prevention vary per step. Refer to each linked MITRE ATT&CK entry under "References" — every technique on that page lists defensive controls, detection telemetry, and known threat-actor usage.

§ Related dossiers