CVE-2026-9602
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Mattermost Desktop App Payload Validation Bypass

Publication date: 2026-07-17

Last updated on: 2026-07-17

Assigner: Mattermost, Inc.

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

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Meta Information

Published
2026-07-17
Last Modified
2026-07-17
Generated
2026-07-17
AI Q&A
2026-07-17
EPSS Evaluated
N/A
NVD
CVE-2026-9602
EUVD
EUVD-2026-45156

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
mattermost desktop_app to 6.2 (inc)
mattermost desktop_app 6.0.2
mattermost desktop_app 5.6.13.0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-400 The product does not properly control the allocation and maintenance of a limited resource.

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Executive Summary

Mattermost Desktop App versions up to 6.2, 6.0.2, and 5.6.13.0 do not properly validate payloads sent from the Mattermost Web App to the Desktop App. This allows a malicious server owner to crash the Desktop App by altering the payload of a method to an invalid format.

Detection Guidance

Detection requires monitoring for crashes in Mattermost Desktop App versions <=6.2, 6.0.2, or 5.6.13.0 when interacting with a malicious server. Check application logs for unexpected terminations or errors during WebSocket communication. Inspect network traffic for malformed payloads from untrusted servers.

Impact Analysis

This vulnerability could allow an attacker who controls a Mattermost server to crash the desktop application of users connected to that server. This disrupts normal use and may lead to denial of service for affected users.

Compliance Impact

The vulnerability allows a malicious server owner to crash the Mattermost Desktop App via malformed payloads, which could lead to denial-of-service conditions. This may impact compliance by disrupting availability of communication tools, potentially violating requirements for continuous access in GDPR or HIPAA environments.

Mitigation Strategies

Update Mattermost Desktop App to a version higher than 6.2, 6.0.2, or 5.6.13.0 to address the payload validation issue.

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