Citrix ADC and Gateway Unauthorized Data Disclosure

name: Citrix ADC and Gateway Unauthorized Data Disclosure
id: b593cac5-dd20-4358-972a-d945fefdaf17
version: 10
creation_date: '2023-10-24'
modification_date: '2026-05-13'
author: Michael Haag, Splunk
status: production
type: TTP
description: The following analytic detects attempts to exploit the Citrix Bleed vulnerability (CVE-2023-4966), which can lead to the leaking of session tokens. It identifies HTTP requests with a 200 status code targeting the /oauth/idp/.well-known/openid-configuration URL endpoint. By parsing web traffic and filtering based on user agent details, HTTP method, source and destination IPs, and sourcetype, it aims to identify potentially malicious requests. This activity is significant for a SOC because successful exploitation can allow attackers to impersonate legitimate users, bypass authentication, and access sensitive data. If confirmed malicious, it could lead to unauthorized data access, network propagation, and critical information exfiltration.
data_source:
    - Suricata
search: |-
    | tstats count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Web
      WHERE Web.url IN ("*/oauth/idp/.well-known/openid-configuration*")  Web.status=200
      BY Web.http_user_agent, Web.status Web.http_method,
         Web.url, Web.url_length, Web.src,
         Web.dest, sourcetype
    | `drop_dm_object_name("Web")`
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `citrix_adc_and_gateway_unauthorized_data_disclosure_filter`
how_to_implement: This detection requires the Web datamodel to be populated from a supported Technology Add-On like Splunk for Apache, Splunk for Nginx, or Splunk for Palo Alto. We recommend hunting in the environment first to understand the scope of the issue and then deploying this detection to monitor for future exploitation attempts. Limit or restrict to Citrix devices only if possible.
known_false_positives: False positives may be present based on organization use of Citrix ADC and Gateway. Filter, or restrict the analytic to Citrix devices only.
references:
    - https://www.assetnote.io/resources/research/citrix-bleed-leaking-session-tokens-with-cve-2023-4966
    - https://github.com/assetnote/exploits/tree/main/citrix/CVE-2023-4966
finding:
    title: Possible exploitation of Citrix Bleed vulnerability against $dest$ fron $src$.
    entity:
        field: dest
        type: system
        score: 50
threat_objects:
    - field: src
      type: ip_address
analytic_story:
    - Citrix NetScaler ADC and NetScaler Gateway CVE-2023-4966
    - Scattered Lapsus$ Hunters
asset_type: Web Server
mitre_attack_id:
    - T1190
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: web
security_domain: network