PYSEC-2026-3824

Dashboard / Vulnerabilities / PYSEC-2026-3824

PYSEC-2026-3824

Summary: django CMS: Page cache ignores plugin-declared Vary headers (disclosure & poisoning)

Details: ### Summary The CMS page cache key ignores the request headers that plugins declare via `get_vary_cache_on()`. The header is added to the response `Vary` header, but the CMS's own cache key does not incorporate the header values, so the first visitor's variant is served to all subsequent visitors regardless of their header values. ### Details `_page_cache_key` (in `cms/cache/page.py`) keys only on cache prefix, site, language, path and timezone. `set_page_cache` collects the plugin-declared vary headers and calls `patch_vary_headers(response, ...)` (affecting only the emitted `Vary` header), but stores and retrieves the cached page under the header-agnostic key. `get_page_cache` therefore returns whichever variant was cached first. ### Impact - **Information disclosure:** when a plugin varies its output on a request header (e.g. `Country-Code`), the variant rendered for the first anonymous visitor is served to everyone until the entry expires, leaking request-specific content across users. - **Cache poisoning:** an unauthenticated attacker can prime the anonymous page cache with content rendered from attacker-chosen header values, which is then served to subsequent visitors. Applies only when `CMS_PAGE_CACHE` is enabled and at least one plugin implements `get_vary_cache_on()`. ### Patches Fixed in 5.0.8: the page cache now folds the request's values implements `get_vary_cache_on()`. ### Patches Fixed in 5.0.8: the page cache now folds the request's values for plugin-declared vary headers into the content key. The set of vary headers is persisted on write and looked up first on read (mirroring Django's `learn_cache_key`/`get_cache_key`); a missing header-list entry degrades to a cache miss, never a wrong-variant hit. ### Workarounds Disable `CMS_PAGE_CACHE`, or avoid plugins that rely on `get_vary_cache_on()`, until upgraded. ### Credits Reported by the security team at the University of Sydney ([@reporter]).

References: https://github.com/django-cms/django-cms/security/advisories/GHSA-fwjf-m4qw-9f2x, https://nvd.nist.gov/vuln/detail/CVE-2026-54625, https://github.com/django-cms/django-cms/pull/8646, https://github.com/django-cms/django-cms/pull/8647, https://github.com/django-cms/django-cms/commit/8758714b865ffa79c6bcd0e5c503958ea48885aa, https://github.com/django-cms/django-cms/commit/d5dc1efa18d157445491c4b12c2dd1efd56f439f, https://github.com/django-cms/django-cms, https://github.com/django-cms/django-cms/releases/tag/5.0.8, https://github.com/django-cms/django-cms/releases/tag/5.1.0, https://pypi.org/project/django-cms, https://github.com/advisories/GHSA-fwjf-m4qw-9f2x