[5.2.x] Fixed CVE-2026-4277 -- Checked add permissions in GenericInlineModelAdmin.

Edit permissions were still checked as part of ordinary form validation,
but because GenericInlineModelAdmin overrides get_formset(), it lacked
InlineModelAdmin's dynamic DeleteProtectedModelForm.has_changed() logic
for checking permissions server-side, leaving the add case unaddressed.

This change reimplements the relevant part of InlineModelAdmin.get_formset().

Thanks N05ec@LZU-DSLab for the report, and Natalia Bidart,
Markus Holtermann, and Simon Charette for reviews.

Backport of ef8b25dcc06d158683a5623ce406d561638f4073 from main.

1 files changed, 10 insertions, 0 deletions

diff --git a/docs/releases/4.2.30.txt b/docs/releases/4.2.30.txt
index 30ffd4eb9d..a6d2deef3c 100644
--- a/docs/releases/4.2.30.txt
+++ b/docs/releases/4.2.30.txt
@@ -26,3 +26,13 @@ behavior of :pypi:`Daphne <daphne>`, the reference server for ASGI.
 
 This issue has severity "low" according to the :ref:`Django security policy
 <security-disclosure>`.
+
+CVE-2026-4277: Privilege abuse in ``GenericInlineModelAdmin``
+=============================================================
+
+Add permissions on inline model instances were not validated on submission of
+forged ``POST`` data in
+:class:`~django.contrib.contenttypes.admin.GenericInlineModelAdmin`.
+
+This issue has severity "low" according to the :ref:`Django security policy
+<security-disclosure>`.