# CVE-2026-12284: Mattermost Desktop App Missing IPC Sender Validation in Calls Leave Handler

> A malicious server can disconnect active calls on other connected servers due to missing IPC sender validation in the Mattermost Desktop App.

- **Severity:** Low 3.8 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 17 Sep 2026
- **Updated:** 17 Sep 2026
- **Also known as:** GHSA-q4vh-9cg5-4q62

## What is CVE-2026-12284?

CVE-2026-12284 is a low-severity missing authorization vulnerability in Mattermost, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Mattermost Desktop App versions <=6.2 6.2.2.0 fails to validate the IPC sender in the leaveCall handler which allows a malicious or compromised Mattermost server (or a user with script access to a connected server view) to disconnect an active call belonging to a different connected server via the desktopAPI.leaveCall IPC message. Mattermost Advisory ID: MMSA-2026-00699

Weakness: CWE-346 (Origin Validation Error)

## Which versions are affected by CVE-2026-12284?

It affects 1 product.


Products: Mattermost Mattermost Desktop.

## How do I fix CVE-2026-12284?

No fix has been published for CVE-2026-12284 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-12284 being exploited?

There is no known exploitation of CVE-2026-12284 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-2026-1046](https://insights.sbomify.com/CVE-2026-1046/): Arbitrary application execution via unvalidated server-controlled URLs in Help menu (high 7.6)
- [CVE-2020-14456](https://insights.sbomify.com/CVE-2020-14456/): Security feature bypass in n/a (high 7.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-12284 and fix it if it is affected.

What it is: CVE-2026-12284 is a low-severity missing authorization vulnerability in Mattermost, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-12284 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-2026-12284/ (Markdown: https://insights.sbomify.com/CVE-2026-12284/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-12284
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-12284
- OSV: https://osv.dev/vulnerability/CVE-2026-12284

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-12284/
Summaries are generated and may contain mistakes; the official description above is the record.