title: Arcadyan Router Exploitations
id: f0500377-bc70-425d-ac8c-e956cd906871
status: test
description: Detects exploitation of vulnerabilities in Arcadyan routers as reported in CVE-2021-20090 and CVE-2021-20091.
references:
    - https://medium.com/tenable-techblog/bypassing-authentication-on-arcadyan-routers-with-cve-2021-20090-and-rooting-some-buffalo-ea1dd30980c2
    - https://www.tenable.com/security/research/tra-2021-13
    - https://blogs.juniper.net/en-us/security/freshly-disclosed-vulnerability-cve-2021-20090-exploited-in-the-wild
author: Bhabesh Raj
date: 2021-08-24
modified: 2023-01-02
tags:
    - attack.initial-access
    - attack.t1190
    - cve.2021-20090
    - cve.2021-20091
    - detection.emerging-threats
logsource:
    category: webserver
detection:
    path_traversal:
        # CVE-2021-20090 (Bypass Auth: Path Traversal)
        cs-uri-query|contains: '..%2f'
    config_file_inj:
        cs-uri-query|contains|all:
            # Chaining of CVE-2021-20090 (Bypass Auth) and CVE-2021-20091 (Config File Injection)
            - '..%2f'
            - 'apply_abstract.cgi'
    noauth_list:
        cs-uri-query|contains:
            - '/images/'
            - '/js/'
            - '/css/'
            - '/setup_top_login.htm'
            - '/login.html'
            - '/loginerror.html'
            - '/loginexclude.html'
            - '/loginlock.html'
    condition: (path_traversal or config_file_inj) and noauth_list
falsepositives:
    - Unknown
level: critical