CVE-2026-34600 Joplin Server delta API returns note content after share access is revoked
Attackers with revoked share access can retrieve private note content via the delta API due to improper authorization checks.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-34600?
CVE-2026-34600 is a medium-severity missing authorization vulnerability in laurent22 joplin, published on 19 May 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
Joplin is an open source note-taking and to-do application that organises notes and lists into notebooks. Versions 3.5.2 and prior contain a logic error in the delta API that allows share recipients to download notes that are no longer shared with them, related to but not fully fixed by the prior patch in #14289. In ChangeModel.delta, when DELTA_INCLUDES_ITEMS is enabled (the default), the latest state of items is attached to delta output without verifying that those items are still shared with the requesting user, and the existing removal logic only filters items deleted for all users. Additionally, the change compression logic incorrectly reduces create - delete to NOOP, which is unsafe because compression is applied per page and an item can have multiple create events; if an earlier create falls on a separate page from a later create -> delete pair, the deletion is dropped and the sequence collapses to a create. As a result, the delta API returns a create event for a deleted item with the full latest content attached, exposing notes the user no longer has access to. This issue has been fixed in version 3.5.3.
Which versions are affected by CVE-2026-34600?
How do I fix CVE-2026-34600?
No fix has been published for CVE-2026-34600 yet. Limit exposure of the affected software until one is available.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-34600 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-34600 exists.
Sources
Also known as GHSA-88x4-77rc-jw94.