ExponentCMS <= 2.6 - Host Header Injection

mediumseverity

4.3CVSS score

2.5%likelihood of exploitation, next 30 days

85%of all CVEs are less likely

Readycheck to confirm it

An HTTP Host header attack exists in ExponentCMS 2.6 and below in /exponent_constants.php. A modified HTTP header can change links on the webpage to an arbitrary value,leading to a possible attack vector for MITM.

Impact

An attacker can manipulate the Host header to perform various attacks, including phishing, session hijacking, and cache poisoning.

Fix

Upgrade ExponentCMS to a version higher than 2.6 or apply the provided patch to fix the Host Header Injection vulnerability.

How to confirm it

Send: GET {{BaseURL}}
Positive when: contains "{{randstr}}.tld" and "EXPONENT.PATH" and "EXPONENT.URL" AND status 200

Run it with nuclei: nuclei -id CVE-2021-38751 -u <target>. This check is not marked as verified by its authors.

The full check

id: CVE-2021-38751

info:
  name: ExponentCMS <= 2.6 - Host Header Injection
  author: dwisiswant0
  severity: medium
  description: An HTTP Host header attack exists in ExponentCMS 2.6 and below in /exponent_constants.php. A modified HTTP header can change links on the webpage to an arbitrary value,leading to a possible attack vector for MITM.
  impact: |
    An attacker can manipulate the Host header to perform various attacks, including phishing, session hijacking, and cache poisoning.
  remediation: |
    Upgrade ExponentCMS to a version higher than 2.6 or apply the provided patch to fix the Host Header Injection vulnerability.
  reference:
    - https://nvd.nist.gov/vuln/detail/CVE-2021-38751
    - https://github.com/exponentcms/exponent-cms/issues/1544
    - https://github.com/exponentcms/exponent-cms/blob/a9fa9358c5e8dc2ce7ad61d7d5bea38505b8515c/exponent_constants.php#L56-L64
    - https://github.com/ARPSyndicate/kenzer-templates
    - https://github.com/ARPSyndicate/cvemon
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
    cvss-score: 4.3
    cve-id: CVE-2021-38751
    cwe-id: CWE-116
    epss-score: 0.02468
    epss-percentile: 0.8463
    cpe: cpe:2.3:a:exponentcms:exponentcms:*:*:*:*:*:*:*:*
  metadata:
    max-request: 1
    vendor: exponentcms
    product: exponentcms
  tags: cve2021,cve,exponentcms,vuln

http:
  - method: GET
    path:
      - "{{BaseURL}}"

    headers:
      Host: '{{randstr}}.tld'

    matchers-condition: and
    matchers:
      - type: word
        part: body
        words:
          - '{{randstr}}.tld'
          - 'EXPONENT.PATH'
          - 'EXPONENT.URL'
        condition: and

      - type: status
        status:
          - 200

References

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