CERT-FR Flags Mattermost Server Vulnerability
CERT-FR advisory warns of an unspecified security flaw in Mattermost Server affecting several version branches; vendor has released patches.
Sourcecert.cyber.gouv.fr — open the original
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CERT-FR has published an advisory regarding a vulnerability in Mattermost Server, a widely used open-source collaboration platform. The vendor (Mattermost) has not publicly disclosed the exact nature of the security issue, only confirming that it allows an attacker to cause an unspecified security impact. No CVE identifier was included in the advisory.
Affected versions include Mattermost Server 11.10.x prior to 11.10.4, 11.11.x prior to 11.11.3, and 11.7.x prior to 11.7.14. Organizations running these versions should consult Mattermost's own security bulletin (MMSA-2026-00759, published 23 October 2026) for further details and apply the corresponding patches as soon as possible. There is no indication in this advisory of active exploitation in the wild, and the risk level was not specified by the vendor.
Defenders should inventory Mattermost Server deployments, confirm version numbers against the affected ranges, and prioritize upgrading to the fixed releases (11.10.4, 11.11.3, or 11.7.14 and later) to remediate the unspecified vulnerability.
Source reporting: https://www.cert.cyber.gouv.fr/avis/CERTFR-2026-AVI-1380
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