# CVE-2021-37864: Users can view the contents of an archived channel when access is explicitly denied by the system admin

> Authenticated users can bypass admin restrictions to view contents of archived channels in Mattermost by directly accessing APIs.

- **Severity:** Low 2.6 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:L/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:** 18 Jan 2022
- **Updated:** 6 Dec 2024
- **Also known as:** GHSA-898c-6fq9-5cv9

## What is CVE-2021-37864?

CVE-2021-37864 is a low-severity missing authorization vulnerability in Mattermost Mattermost, published on 18 Jan 2022. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

Mattermost 6.1 and earlier fails to sufficiently validate permissions while viewing archived channels, which allows authenticated users to view contents of archived channels even when this is denied by system administrators by directly accessing the APIs.

Weakness: CWE-863 (Incorrect Authorization), CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2021-37864?

It affects 1 product.


Products: Mattermost Mattermost.

## How do I fix CVE-2021-37864?

No fix has been published for CVE-2021-37864 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-37864 being exploited?

There is no known exploitation of CVE-2021-37864 in the wild and no public exploit code.

## Other vulnerabilities in Mattermost Mattermost

- [CVE-2019-20851](https://insights.sbomify.com/CVE-2019-20851/): Path traversal in n/a (critical 9.1)
- [CVE-2024-39274](https://insights.sbomify.com/CVE-2024-39274/): Malicious remote can add users to arbitrary teams and channels (high 8.7)
- [CVE-2024-39777](https://insights.sbomify.com/CVE-2024-39777/): Malicious remote can invite itself to an arbitrary local channel (high 8.7)
- [CVE-2024-39830](https://insights.sbomify.com/CVE-2024-39830/): Timing attack during remote cluster token comparison when shared channels are enabled (high 8.1)
- [CVE-2023-3615](https://insights.sbomify.com/CVE-2023-3615/): Lack of server certificate validation in websockets connection (high 8.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-37864 and fix it if it is affected.

What it is: CVE-2021-37864 is a low-severity missing authorization vulnerability in Mattermost Mattermost, published on 18 Jan 2022. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-37864 in the wild and no public exploit code.

Affected product: Mattermost Mattermost. 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-2021-37864/ (Markdown: https://insights.sbomify.com/CVE-2021-37864/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-37864
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-37864
- OSV: https://osv.dev/vulnerability/CVE-2021-37864

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-37864/
Summaries are generated and may contain mistakes; the official description above is the record.