# CVE-2026-9602: Mattermost Desktop App crashes when malformed arguments are provided to some exposed IPC methods

> A malicious server owner can crash the Mattermost Desktop App by sending malformed arguments to exposed IPC methods.

- **Severity:** Medium 5.7 (`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:** 17 Jul 2026
- **Updated:** 17 Jul 2026
- **Also known as:** GHSA-82vr-gjvh-q9r8

## What is CVE-2026-9602?

CVE-2026-9602 is a medium-severity denial of service vulnerability in Mattermost, published on 17 Jul 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Mattermost Desktop App versions <=6.2 6.0.2 5.6.13.0 fail to validate payloads sent from the Mattermost Web App to the Desktop App which allows a malicious server owner to crash the Mattermost Desktop App via changing the payload of a method to a malformed one. Mattermost Advisory ID: MMSA-2026-00678

Weakness: CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-9602?

It affects 1 product.


Products: Mattermost Mattermost Desktop.

## How do I fix CVE-2026-9602?

No fix has been published for CVE-2026-9602 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-9602 being exploited?

There is no known exploitation of CVE-2026-9602 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-2026-9602 and fix it if it is affected.

What it is: CVE-2026-9602 is a medium-severity denial of service vulnerability in Mattermost, published on 17 Jul 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-2026-9602 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-2026-9602/ (Markdown: https://insights.sbomify.com/CVE-2026-9602/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-9602
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-9602
- OSV: https://osv.dev/vulnerability/CVE-2026-9602

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-9602/
Summaries are generated and may contain mistakes; the official description above is the record.