CVE-2026-35193: Django: UpdateCacheMiddleware may disclose private cached responses by omitting Authorization from Vary

An issue was discovered in Django 5.2 before 5.2.15 and 6.0 before 6.0.6. django.middleware.cache.UpdateCacheMiddleware in Django does not add Authorization to the Vary response header for requests bearing that header without Cache-Control: public, which allows remote attackers to read private cached responses via unauthenticated requests to the same URL. Earlier, unsupported Django series (such as 5.0.x, 4.1.x, and 3.2.x) were not evaluated and may also be affected. Django would like to thank Shai Berger for reporting this issue.