GHSA-mh4x-rmrx-3hp4 Mattermost has session spoofing due to lack of single-use consumption of guest magic link tokens enforcement

• Go github.com/mattermost/mattermost/server/v8: >= 8.0.0-20250721062209-4952acea88ce, < 8.0.0-20250723052842-4cb8d8940332 → fixed in 8.0.0-20250723052842-4cb8d8940332 • Go github.com/mattermost/mattermost-server: >= 10.11.0-rc1, < 10.11.13 → fixed in 10.11.13 • Go github.com/mattermost/mattermost-server: >= 11.5.0-rc1, < 11.5.0 → fixed in 11.5.0 • Go github.com/mattermost/mattermost-server: >= 11.4.0-rc1, < 11.4.3 → fixed in 11.4.3 • Go github.com/mattermost/mattermost-server: >= 11.3.0-rc1, < 11.3.3 → fixed in 11.3.3

Mattermost versions 10.11.x <= 10.11.12, 11.5.x <= 11.5.0, 11.4.x <= 11.4.2, 11.3.x <= 11.3.2 fail to enforce atomic single-use consumption of guest magic link tokens, which allows an attacker with access to a valid magic link to establish multiple independent authenticated sessions via concurrent requests. Mattermost Advisory ID: MMSA-2026-00624.