CVE-2026-63003: django CMS Broken Access Control Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-6x92-6vx4-5fwr",
  "modified" : "2026-08-20T18:42:44Z",
  "published" : "2026-08-20T18:42:44Z",
  "aliases" : [ "CVE-2026-63003" ],
  "summary" : "django CMS: Broken access control in page *Duplicate* allows reading the content of any page (cross-site / restriction bypass)",
  "details" : "## Impact\n\nThe only authorization gate on the duplicate flow is `PageAdmin.has_add_permission`,\nwhich checks `user_can_add_page(user, site)` / `user_can_add_subpage(...)` — i.e. *“may\nthis user create a page at all”*. Nothing checks the user’s relationship to the page being\ncopied:\n\n- `cms/admin/forms.py` — `DuplicatePageForm.source = ModelChoiceField(queryset=Page.objects.all(), widget=HiddenInput())`\n  spans **every page in the database, on every site**.\n- `cms/admin/forms.py` — `AddPageForm.__init__` returns early when the `source` widget is\n  hidden, so the queryset is **never narrowed** to the user’s site/subtree.\n- `cms/admin/forms.py` — `AddPageForm.clean()` validates only URL uniqueness; `source` is\n  never validated against the user.\n- `cms/admin/pageadmin.py` — `duplicate()` seeds `source` from the URL **only on GET**; on\n  POST the value comes entirely from the request body.\n- `cms/admin/forms.py` — `AddPageForm.save()` → `from_source()` performs\n  `source.copy(..., permissions=False)` and copies **every placeholder and all plugins** of\n  `source` into a new page on the attacker’s site. Because `permissions=False` drops the\n  source’s view restrictions, the resulting copy is fully readable by the attacker.\n\nThis crosses a real privilege boundary: a staff user restricted (via `CMS_PERMISSION`) to\ntheir own site or subtree can exfiltrate the content of restricted pages and of pages\nbelonging to other tenants.\n\n**Read-back is trivial (verified):** the copy is created on the attacker’s site and, because\n`copy(..., permissions=False)` strips the source’s view restrictions, the new page is\n*unrestricted*. `user_can_view_page()` then returns `True` for it (unrestricted +\n`PUBLIC_FOR`), so the attacker — or even an anonymous visitor — can read the duplicated\ncontent directly from the front end. No further permission on the new page is required.\n\n## Proof of concept\n\n1. Log in as a staff user `attacker` who has *add page* permission but **no** view/change\n   permission on a target (secret / other-site) page `SECRET_ID`.\n2. Send (the URL `<id>` only needs to be a `PageContent` the attacker can already see —\n   e.g. one of their own pages; the victim id goes in the POST body):\n\n```http\nPOST /admin/cms/pagecontent/<MY_OWN_PAGECONTENT_ID>/duplicate/ HTTP/1.1\nCookie: sessionid=<attacker session>\nContent-Type: application/x-www-form-urlencoded\n\ncsrfmiddlewaretoken=...&title=x&slug=x&language=en&source=<SECRET_ID>\n```\n\n3. A new, unrestricted page is created under the attacker’s site containing a verbatim\n   copy of the secret page’s plugins, which the attacker can now preview/edit/read.\n\n## Patches \n\nEnforce an object-level permission check on `source`:\n\n```python\nclass DuplicatePageForm(AddPageForm):\n    source = forms.ModelChoiceField(\n        queryset=Page.objects.all(),\n        required=True,\n        widget=forms.HiddenInput(),\n    )\n\n    def clean_source(self):\n        source = self.cleaned_data.get(\"source\")\n        if source and not user_can_view_page(self._user, source):\n            raise ValidationError(_(\"You do not have permission to copy this page.\"))\n        return source\n```\n\n(`user_can_view_page` is imported from `cms.utils.page_permissions`.)\n\n## Workarounds\n\nUntil patched, restrict access to the `cms.add_page` permission to fully-trusted staff, or\ndisable the duplicate action for delegated/limited editors.\n\n## References\n\n- `cms/admin/pageadmin.py` — `duplicate()`, `has_add_permission()`, `get_urls()`\n- `cms/admin/forms.py` — `DuplicatePageForm`, `AddPageForm.__init__/clean/save/from_source`\n- Regression tests: `cms/tests/test_forms.py::DuplicatePageFormSecurityTestCase`",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "django-cms"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.0.9"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 5.0.8"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/django-cms/django-cms/security/advisories/GHSA-6x92-6vx4-5fwr"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/django-cms/django-cms/pull/8713"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/django-cms/django-cms/commit/3e1ccf7573eb1a74ebbbfaaa812c1f5cadf14e6c"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/django-cms/django-cms"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/django-cms/django-cms/releases/tag/5.0.9"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-639", "CWE-862" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-20T18:42:44Z",
    "nvd_published_at" : null
  }
}