# CVE-2026-3117: Instance and webhook GitLab plugin commands were able to be run by non-admin users

> Non-admin users can execute privileged GitLab plugin commands to uninstall instances or configure webhooks due to missing permission checks.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **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:** 18 May 2026
- **Updated:** 18 May 2026
- **Also known as:** GHSA-5gjv-5xhr-vc35

## What is CVE-2026-3117?

CVE-2026-3117 is a medium-severity missing authorization vulnerability in Mattermost Mattermost Server, published on 18 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Mattermost Plugins versions <=11.5 11.1.5 10.13.11 11.3.4.0 fail to properly check for permissions when processing commands in the Gitlab plugin which allows normal users to uninstall instances or setup webhook connections via the {{gitlab instance {option}}} or the {{/gitlab webhook {option}}} commands. Mattermost Advisory ID: MMSA-2026-00600

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2026-3117?

It affects 1 product.


Products: Mattermost Mattermost Server.

## How do I fix CVE-2026-3117?

No fix has been published for CVE-2026-3117 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-3117 being exploited?

There is no known exploitation of CVE-2026-3117 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-2026-3117 and fix it if it is affected.

What it is: CVE-2026-3117 is a medium-severity missing authorization vulnerability in Mattermost Mattermost Server, published on 18 May 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-2026-3117 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-2026-3117/ (Markdown: https://insights.sbomify.com/CVE-2026-3117/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3117
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3117
- OSV: https://osv.dev/vulnerability/CVE-2026-3117

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-3117/
Summaries are generated and may contain mistakes; the official description above is the record.