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

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

Which versions are affected by CVE-2026-9602?

It affects 1 product.

Products include 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.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

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 Code injection in n/a Critical 9.8
• CVE-2019-20856 Code injection in n/a Critical 9.8
• CVE-2019-20861 Code injection in n/a High 8.8
• CVE-2026-1046 Arbitrary application execution via unvalidated server-controlled URLs in Help menu High 7.6
• CVE-2020-14456 Security feature bypass in n/a High 7.3

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-82vr-gjvh-q9r8.