Flask is a lightweight WSGI web application framework. When all of the following conditions are met, a response containing data intended for one client may be cached and subsequently sent by the proxy to other clients. If the proxy also caches `Set-Cookie` headers, it may send one client's `session` cookie to other clients. The severity depends on the application's use of the session and the proxy's behavior regarding cookies. The risk depends on all these conditions being met. 1. The application must be hosted behind a caching proxy that does not strip cookies or ignore responses with cookies. 2. The application sets `session.permanent = True` 3. The application does not access or modify the session at any point during a request. 4. `SESSION_REFRESH_EACH_REQUEST` enabled (the default). 5. The application does not set a `Cache-Control` header to indicate that a page is private or should not be cached. This happens because vulnerable versions of Flask only set the `Vary: Cookie` header when the session is accessed or modified, not when it is refreshed (re-sent to update the expiration) without being accessed or modified. This issue has been fixed in versions 2.3.2 and 2.2.5.
Created python-flask tracking bugs for this issue: Affects: fedora-all [bug 2196644] Affects: openstack-rdo [bug 2196645]
upstream commit: https://github.com/pallets/flask/commit/70f906c51ce49c485f1d355703e9cc3386b1cc2b
Created python3-flask tracking bugs for this issue: Affects: epel-7 [bug 2196676]
This issue has been addressed in the following products: Red Hat OpenStack Platform 17.0 Via RHSA-2023:3440 https://access.redhat.com/errata/RHSA-2023:3440
This issue has been addressed in the following products: Red Hat OpenStack Platform 16.2 Via RHSA-2023:3444 https://access.redhat.com/errata/RHSA-2023:3444
This issue has been addressed in the following products: Red Hat OpenStack Platform 16.1 Via RHSA-2023:3446 https://access.redhat.com/errata/RHSA-2023:3446
This issue has been addressed in the following products: Red Hat Enterprise Linux 7 Extras Via RHSA-2023:3525 https://access.redhat.com/errata/RHSA-2023:3525
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s): https://access.redhat.com/security/cve/cve-2023-30861
This issue has been addressed in the following products: Red Hat OpenShift Container Platform 4.13 Via RHSA-2023:3536 https://access.redhat.com/errata/RHSA-2023:3536
This issue has been addressed in the following products: Red Hat OpenShift Container Platform 4.12 Via RHSA-2023:3545 https://access.redhat.com/errata/RHSA-2023:3545
This issue has been addressed in the following products: Red Hat Quay 3 Via RHSA-2023:7341 https://access.redhat.com/errata/RHSA-2023:7341