# CVE-2026-1046: Arbitrary application execution via unvalidated server-controlled URLs in Help menu

> A malicious server can execute arbitrary code on a user's system by providing unvalidated URLs in the Help menu of the Mattermost Desktop App.

- **Severity:** High 7.6 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:N/A:L`)
- **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:** 16 Feb 2026
- **Updated:** 17 Feb 2026
- **Also known as:** GHSA-gjx5-j34g-5g5p

## What is CVE-2026-1046?

CVE-2026-1046 is a high-severity command injection vulnerability in Mattermost, published on 16 Feb 2026. 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 Desktop App versions <=6.0 6.2.0 5.2.13.0 fail to validate help links which allows a malicious Mattermost server to execute arbitrary executables on a user’s system via the user clicking on certain items in the Help menu Mattermost Advisory ID: MMSA-2026-00577

Weakness: CWE-939 (Improper Authorization in Handler for Custom URL Scheme)

## Which versions are affected by CVE-2026-1046?

It affects 1 product.


Products: Mattermost Mattermost Desktop.

## How do I fix CVE-2026-1046?

No fix has been published for CVE-2026-1046 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-1046 being exploited?

There is no known exploitation of CVE-2026-1046 in the wild and no public exploit code.

## Other vulnerabilities in Mattermost

- [CVE-2016-11064](https://insights.sbomify.com/CVE-2016-11064/): Code injection in n/a (critical 9.8)
- [CVE-2019-20856](https://insights.sbomify.com/CVE-2019-20856/): Code injection in n/a (critical 9.8)
- [CVE-2019-20861](https://insights.sbomify.com/CVE-2019-20861/): Code injection in n/a (high 8.8)
- [CVE-2020-14456](https://insights.sbomify.com/CVE-2020-14456/): Security feature bypass in n/a (high 7.3)
- [CVE-2026-8075](https://insights.sbomify.com/CVE-2026-8075/): Posting a malicious markdown image crashes the Mattermost Desktop App (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-1046 and fix it if it is affected.

What it is: CVE-2026-1046 is a high-severity command injection vulnerability in Mattermost, published on 16 Feb 2026. 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-2026-1046 in the wild and no public exploit code.

Affected product: 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-2026-1046/ (Markdown: https://insights.sbomify.com/CVE-2026-1046/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-1046
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-1046
- OSV: https://osv.dev/vulnerability/CVE-2026-1046

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-1046/
Summaries are generated and may contain mistakes; the official description above is the record.