# CVE-2026-26230: Team Admin Privilege Escalation to Demote Members to Guest

> Team administrators can improperly demote members to guest role due to insufficient permission validation in the API.

- **Severity:** Low 3.8 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Mar 2026
- **Updated:** 17 Mar 2026
- **Also known as:** GHSA-q6ph-8227-6m8x

## What is CVE-2026-26230?

CVE-2026-26230 is a low-severity vulnerability in Mattermost Mattermost Server, published on 16 Mar 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

Mattermost versions 10.11.x <= 10.11.10 fail to properly validate permission requirements in the team member roles API endpoint which allows team administrators to demote members to guest role. Mattermost Advisory ID: MMSA-2025-00531

Weakness: CWE-863 (Incorrect Authorization)

## Which versions are affected by CVE-2026-26230?

It affects 1 product.


Products: Mattermost Mattermost Server.

## How do I fix CVE-2026-26230?

No fix has been published for CVE-2026-26230 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-26230 being exploited?

There is no known exploitation of CVE-2026-26230 in the wild and no public exploit code.

## Other vulnerabilities in Mattermost Mattermost Server

- [CVE-2025-12419](https://insights.sbomify.com/CVE-2025-12419/): Account takeover on OAuth/OpenID-enabled servers (critical 9.9)
- [CVE-2025-12421](https://insights.sbomify.com/CVE-2025-12421/): Account Takeover via Code Exchange Endpoint (critical 9.9)
- [CVE-2025-4981](https://insights.sbomify.com/CVE-2025-4981/): Path Traversal Leading to RCE by Any Authenticated Mattermost User (critical 9.9)
- [CVE-2025-20051](https://insights.sbomify.com/CVE-2025-20051/): Arbitrary file read via block duplication in Mattermost Boards (critical 9.9)
- [CVE-2025-25279](https://insights.sbomify.com/CVE-2025-25279/): Arbitrary file read in Mattermost Boards via import & export board archive (critical 9.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-26230 and fix it if it is affected.

What it is: CVE-2026-26230 is a low-severity vulnerability in Mattermost Mattermost Server, published on 16 Mar 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-26230 in the wild and no public exploit code.

Affected product: Mattermost Mattermost 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-2026-26230/ (Markdown: https://insights.sbomify.com/CVE-2026-26230/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-26230
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-26230
- OSV: https://osv.dev/vulnerability/CVE-2026-26230

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-26230/
Summaries are generated and may contain mistakes; the official description above is the record.