# CVE-2026-8075: Mattermost Desktop App denial of service via malicious image link

Source: https://junglewise.ai/threats/cve-2026-8075-mattermost-desktop-app-denial-of-service-via-malicious-image-link  
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-2026-8075 · Severity: medium · CVSS 6.5 · Published 2026-07-17

Mattermost is a collaboration and messaging platform used by organizations for internal communication. A vulnerability in the Mattermost Desktop App allows a user to crash the application of other members in a channel by posting a specially crafted link containing a malicious image. This can lead to service disruptions and prevent team members from accessing their communications until the application is restarted.

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

## Quick answers

**Is CVE-2026-8075 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-8075 being exploited in the wild.

**How severe is CVE-2026-8075?** Medium severity, with a CVSS score of 6.5, published 17 July 2026.

**Which products and versions are affected?** Mattermost Desktop App <=6.2, 5.5.13, 6.0.2.0.

**Is there a fix for CVE-2026-8075?** 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-2026-8075 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-8075?** 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 improper check for unusual or exceptional conditions (CWE-754) specifically related to a missing null check during header validation. An authenticated attacker can exploit this by posting a malicious link with an embedded image that lacks specific expected headers. When other channel members' desktop clients attempt to process the image, the lack of a null check causes the application to crash. This is a remote denial-of-service attack requiring low privileges (standard user account) and no user interaction beyond the client attempting to render the malicious post. Fixes are available in versions 6.3.0, 5.13.6.0, and 6.2.1.0.

## Affected products

- Mattermost Mattermost Desktop App <=6.2, 5.5.13, 6.0.2.0

## Timeline

- 2026-07-17: advisory: Mattermost Advisory MMSA-2026-00668 published.
- 2026-07-17: disclosed: CVE-2026-8075 published to the NVD.

## References

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

## Related threats

- [Mattermost Desktop App URL scheme validation bypass](https://junglewise.ai/threats/cve-2026-75588-mattermost-desktop-app-url-scheme-validation-bypass)
- [Mattermost Desktop App IPC validation bypass in leaveCall handler](https://junglewise.ai/threats/cve-2026-12284-mattermost-desktop-app-ipc-validation-bypass-in-leavecall-handler)
- [Mattermost Desktop App content restriction bypass](https://junglewise.ai/threats/cve-2026-75025-mattermost-desktop-app-content-restriction-bypass)
- [Mattermost Desktop App denial of service via malformed payload](https://junglewise.ai/threats/cve-2026-9602-mattermost-desktop-app-denial-of-service-via-malformed-payload)
- [Mattermost Desktop App denial of service via long URLs](https://junglewise.ai/threats/cve-2026-8683-mattermost-desktop-app-denial-of-service-via-long-urls)