# CVE-2021-37866: Session is not invalidated on server-side when user logged out of Boards

> Attackers can reuse old session tokens after logout to maintain unauthorized access to Mattermost Boards accounts.

- **Severity:** Medium 4.7 (`CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **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-g28x-633f-r8qf

## What is CVE-2021-37866?

CVE-2021-37866 is a medium-severity authentication bypass vulnerability in Mattermost Boards, published on 18 Jan 2022. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

Mattermost Boards plugin v0.10.0 and earlier fails to invalidate a session on the server-side when a user logged out of Boards, which allows an attacker to reuse old session token for authorization.

Weakness: CWE-613 (DEPRECATED: Insufficient Session Expiration)

## Which versions are affected by CVE-2021-37866?

It affects 1 product.


Products: Mattermost Mattermost Boards.

## How do I fix CVE-2021-37866?

No fix has been published for CVE-2021-37866 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-37866 being exploited?

There is no known exploitation of CVE-2021-37866 in the wild and no public exploit code.

## Other vulnerabilities in Mattermost Boards

- [CVE-2021-37867](https://insights.sbomify.com/CVE-2021-37867/): Emails of all users are exposed via one of the Boards APIs (medium 4.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-37866 and fix it if it is affected.

What it is: CVE-2021-37866 is a medium-severity authentication bypass vulnerability in Mattermost Boards, published on 18 Jan 2022. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-37866 in the wild and no public exploit code.

Affected product: Mattermost Boards. 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-2021-37866/ (Markdown: https://insights.sbomify.com/CVE-2021-37866/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-37866
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-37866
- OSV: https://osv.dev/vulnerability/CVE-2021-37866

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-37866/
Summaries are generated and may contain mistakes; the official description above is the record.