CVE-2026-34213 Docmost has cross-page attachment overwrite via flawed attachmentId overwrite validation

Medium 5.4 Published 14 Apr 2026 Updated 15 Apr 2026

An authenticated user can overwrite attachments on other pages in the same workspace by manipulating attachment IDs, compromising data integrity.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

What is CVE-2026-34213?

CVE-2026-34213 is a medium-severity missing authorization vulnerability in docmost, published on 14 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

Docmost is open-source collaborative wiki and documentation software. Starting in version 0.3.0 and prior to version 0.71.0, improper authorization in Docmost allows a low-privileged authenticated user to overwrite another page's attachment within the same workspace by supplying a victim `attachmentId` to `POST /api/files/upload`. This is a remote integrity issue requiring no victim interaction. Version 0.71.0 contains a patch.

Weakness: CWE-639

Which versions are affected by CVE-2026-34213?

It affects 1 product.

Products include Docmost Docmost.

How do I fix CVE-2026-34213?

No fix has been published for CVE-2026-34213 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-2026-34213 being exploited?

There is no known exploitation of CVE-2026-34213 in the wild and no public exploit code.

Public exploit code: 1 proofs of concept on GitHub.

Sources

Also known as GHSA-89fp-2hch-j9gp.