Mattermost Desktop App patches multiple flaws
CERT-FR advises patching multiple unspecified vulnerabilities in Mattermost Desktop App versions before 6.2.4, 6.3.1, and 6.4.
Sourcecert.ssi.gouv.fr — open the original
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CERT-FR has issued an advisory covering multiple vulnerabilities affecting the Mattermost Desktop App. Affected versions include the 6.2.x branch prior to 6.2.4, the 6.3.x branch prior to 6.3.1, and all versions prior to 6.4. The vendor has not specified the exact nature of the security impact in the public bulletin referenced by CERT-FR, only indicating that an attacker could cause an unspecified security issue.
No information is provided regarding active exploitation in the wild. Defenders running Mattermost Desktop App should consult Mattermost's own security bulletins (MMSA-2026-00778 and MMSA-2026-00779, both dated 15 October 2026) for technical details and apply the available patches by upgrading to version 6.4 or later, or to the fixed point releases 6.2.4 / 6.3.1 depending on the branch in use.
Given the lack of detail on exploitability, impact, or in-the-wild activity, this should be treated as a standard patch-management advisory rather than an urgent incident response matter. Organizations using Mattermost Desktop App as a collaboration tool should prioritize the update during routine patch cycles.
Source reporting: https://www.cert.ssi.gouv.fr/avis/CERTFR-2026-AVI-1328
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