# CVE-2026-9602: Mattermost Desktop App denial of service via malformed payload

Source: https://junglewise.ai/threats/cve-2026-9602-mattermost-desktop-app-denial-of-service-via-malformed-payload  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-17. Updated: 2026-07-17  
License: CC BY 4.0 with a link back

CVE-2026-9602 · Severity: medium · CVSS 6.5 · Published 2026-07-17

A vulnerability in the Mattermost Desktop App allows a malicious server owner to crash the application on a user's computer. This occurs because the desktop software does not properly check the data it receives from the web server. An exploit would result in a denial of service, preventing employees from using the communication platform until the application is restarted or patched.

Technologies: [Mattermost Desktop App](https://junglewise.ai/threats/technologies/desktop-app). Vendors: [Mattermost](https://junglewise.ai/threats/vendors/mattermost).

## Quick answers

**Is CVE-2026-9602 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-9602 being exploited in the wild.

**How severe is CVE-2026-9602?** Medium severity, with a CVSS score of 6.5, published 17 July 2026.

**Which products and versions are affected?** Mattermost Desktop App <=6.2, 6.0.2, 5.6.13.0.

**Is there a fix for CVE-2026-9602?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-9602 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-9602?** Check whether you run Mattermost Desktop App at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The Mattermost Desktop App suffers from an uncontrolled resource consumption vulnerability (CWE-400) due to insufficient validation of payloads sent from the Mattermost Web App. A malicious server administrator can send a malformed method payload to the client application, triggering a crash. This is a network-based attack requiring low privileges (server owner status) but no user interaction. The vulnerability is addressed in versions 6.3.0, 6.2.1.0, and 5.13.7.0.

## Affected products

- Mattermost Desktop App <=6.2, 6.0.2, 5.6.13.0

## Timeline

- 2026-07-17: disclosed
- 2026-07-17: advisory

## References

- [https://mattermost.com/security-updates](https://mattermost.com/security-updates)

## Related threats

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