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 clients session cookie to other clients. The severity depends on the applications use of the session and the proxys behavior regarding cookies. The risk depends on all these conditions being met.
session.permanent = TrueSESSION_REFRESH_EACH_REQUEST enabled (the default).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.
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| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Flask | Palletsprojects | * | 2.2.5 (excluding) |
| Flask | Palletsprojects | 2.3.0 (including) | 2.3.2 (excluding) |