# CVE-2023-25821: Nextcloud download permissions can be changed by resharer

> Attackers can bypass secure view restrictions on internal shares by exploiting reshare permissions, allowing unauthorized data access.

- **Severity:** Medium 5.7 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N`)
- **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 available:** No
- **Published:** 24 Feb 2023
- **Updated:** 10 Mar 2025
- **Also known as:** GHSA-7w6h-5qgw-4j94

## What is CVE-2023-25821?

CVE-2023-25821 is a medium-severity missing authorization vulnerability in Nextcloud Nextcloud Server, published on 24 Feb 2023. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

Nextcloud is an Open Source private cloud software. Versions 24.0.4 and above, prior to 24.0.7, and 25.0.0 and above, prior to 25.0.1, contain Improper Access Control. Secure view for internal shares can be circumvented if reshare permissions are also given. This issue is patched in versions 24.0.7 and 25.0.1. No workaround  is available.

Weakness: CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2023-25821?

It affects 1 product.


Products: Nextcloud Nextcloud Server.

## How do I fix CVE-2023-25821?

No fix has been published for CVE-2023-25821 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-25821 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-25821 exists.

## 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-2023-25821 and fix it if it is affected.

What it is: CVE-2023-25821 is a medium-severity missing authorization vulnerability in Nextcloud Nextcloud Server, published on 24 Feb 2023. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-25821 exists.

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-2023-25821/ (Markdown: https://insights.sbomify.com/CVE-2023-25821/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-25821
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-25821
- OSV: https://osv.dev/vulnerability/CVE-2023-25821

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-25821/
Summaries are generated and may contain mistakes; the official description above is the record.