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

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

- **Severity:** Medium 5.4 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 14 Apr 2026
- **Updated:** 15 Apr 2026
- **Also known as:** GHSA-89fp-2hch-j9gp

## 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 (Authorization Bypass Through User-Controlled Key)

## Which versions are affected by CVE-2026-34213?

It affects 1 product.


Products: 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.

## 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:

- A low-privileged Docmost user could supply a victim attachmentId to the generic upload endpoint and overwrite another page's stored attachment inside the same workspace. (github_poc): https://github.com/0xmrma/CVE-2026-34213

## Other vulnerabilities in docmost

- [CVE-2026-24045](https://insights.sbomify.com/CVE-2026-24045/): Docmost Affected by Stored XSS in Public Share Page (high 7.3)
- [CVE-2026-22249](https://insights.sbomify.com/CVE-2026-22249/): Docmost affected by an Arbitrary File Write via Zip Import Feature (ZipSlip) (high 7.1)
- [CVE-2026-23630](https://insights.sbomify.com/CVE-2026-23630/): Docmost is vulnerable to stored Cross-Site Scripting (XSS) through Mermaid rendering (medium 6.3)
- [CVE-2025-55574](https://insights.sbomify.com/CVE-2025-55574/): Cross-site scripting in n/a (medium 6.1)
- [CVE-2026-40927](https://insights.sbomify.com/CVE-2026-40927/): Docmost: XSS in Comments with JavaScript URI (medium 5.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-34213 and fix it if it is affected.

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

Affected product: docmost. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-34213/ (Markdown: https://insights.sbomify.com/CVE-2026-34213/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-34213
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-34213
- OSV: https://osv.dev/vulnerability/CVE-2026-34213

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-34213/
Summaries are generated and may contain mistakes; the official description above is the record.