# CVE-2026-45283: Nextcloud: Files Lock app allows users to lock and unlock files of other users

> Authenticated users can lock or unlock other users' files and bypass token-based locks due to improper ownership validation in the Files Lock app.

- **Severity:** Medium 6.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/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:** 1 Jun 2026
- **Updated:** 1 Jun 2026
- **Also known as:** GHSA-4chh-6mhf-p4jj

## What is CVE-2026-45283?

CVE-2026-45283 is a medium-severity missing authorization vulnerability in Nextcloud Nextcloud Server, published on 1 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Nextcloud is an open source content collaboration platform. In Nextcloud Server from versions 32.0.0 to before 32.0.2, and 33.0.0 to before 33.0.1, the files_lock app did not properly validate the ownership of files when processing DAV lock and unlock requests. An authenticated user could lock or unlock files belonging to other users by targeting their absolute WebDAV paths. Additionally, lock tokens were disclosed to unauthorized callers in error responses, allowing attackers to remove token-based locks placed by other users' client applications. It is recommended that the Nextcloud Server is upgraded to 32.0.2 or 33.0.1. It is recommended that the Nextcloud Enterprise Server is upgraded to 31.0.14.4 or 32.0.2 or 33.0.1

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-45283?

It affects 1 product.


Products: Nextcloud Nextcloud Server.

## How do I fix CVE-2026-45283?

No fix has been published for CVE-2026-45283 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-45283 being exploited?

There is no known exploitation of CVE-2026-45283 in the wild and no public exploit code.

## Other vulnerabilities in Nextcloud Nextcloud Server

- [CVE-2021-32802](https://insights.sbomify.com/CVE-2021-32802/): Preview generation used third-party library not suited for user-generated content in Nextcloud server (critical 9.3)
- [CVE-2023-26482](https://insights.sbomify.com/CVE-2023-26482/): Scope of workflow operations is not validated in nextcloud server (critical 9.1)
- [CVE-2018-3775](https://insights.sbomify.com/CVE-2018-3775/): Auth bypass in Nextcloud Server (high 8.8)
- [CVE-2023-35172](https://insights.sbomify.com/CVE-2023-35172/): Nextcloud Server password reset endpoint is not brute force protected (high 8.7)
- [CVE-2023-32320](https://insights.sbomify.com/CVE-2023-32320/): Nextcloud Server's brute force protection allows someone to send more requests than intended (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-45283 and fix it if it is affected.

What it is: CVE-2026-45283 is a medium-severity missing authorization vulnerability in Nextcloud Nextcloud Server, published on 1 Jun 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-2026-45283 in the wild and no public exploit code.

Affected product: Nextcloud Nextcloud Server. 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-2026-45283/ (Markdown: https://insights.sbomify.com/CVE-2026-45283/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45283
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45283
- OSV: https://osv.dev/vulnerability/CVE-2026-45283

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45283/
Summaries are generated and may contain mistakes; the official description above is the record.