GHSA-fwjf-m4qw-9f2x is a medium-severity (CVSS 4.8) vulnerability in django-cms. O3 Security confirms whether GHSA-fwjf-m4qw-9f2x is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
django CMS: Page cache ignores plugin-declared Vary headers (disclosure & poisoning)
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-fwjf-m4qw-9f2x.
Real-World Exposure
django-cmsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
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]).
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | django-cms | all versions | 5.0.8 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for django-cms. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update django-cms to 5.0.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fwjf-m4qw-9f2x is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-fwjf-m4qw-9f2x is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-fwjf-m4qw-9f2x. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-fwjf-m4qw-9f2x in your dependencies?
O3 detects GHSA-fwjf-m4qw-9f2x across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.