CVE-2026-28759

Insufficient authorization in shared channel membership sync allows remote cluster to remove users from arbitrary channels

CVSS 4.3 MEDIUMEPSS 0.2%CWE-863

Vexday Risk Score

13Baixo

Decisão SSVC (CISA)

Track

Sem sinal de exploração → monitorar

CVSS 4.3EPSS 0.2%KEV nãoPoC —Nuclei —Metasploit —Patch referenciado

Ciclo de vida

18 mai 2026Publicada no NVD

Recomendação: Monitorar — sem sinal de exploração no momento.

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to validate that a remote cluster has access to a channel before processing membership removal requests during shared channel membership sync, which allows a malicious remote cluster to remove any user from any channel, including private channels, via crafted membership sync messages targeting channels the remote cluster is not authorized to access. Mattermost Advisory ID: MMSA-2026-00576

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

Produtos afetados

Mattermost · Mattermost

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Referências

https://mattermost.com/security-updates