Description
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
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mattermost | Mattermost | 10.11.0 – ≤ 10.11.12, 11.5.0 – ≤ 11.5.0, 11.4.0 – ≤ 11.4.2, 11.3.0 – ≤ 11.3.2 | 11.6.0 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Leap 16.0 | govulncheck-vulndb | 0.0.20260723T184607-160000.1.1 | openSUSE-SU-2026:21483-1 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | >= 10.11.0-rc1, < 10.11.13 | 10.11.13 | GHSA-mh4x-rmrx-3hp4 |
| Go | github.com/mattermost/mattermost-server | >= 11.5.0-rc1, < 11.5.0 | 11.5.0 | GHSA-mh4x-rmrx-3hp4 |
| Go | github.com/mattermost/mattermost-server | >= 11.4.0-rc1, < 11.4.3 | 11.4.3 | GHSA-mh4x-rmrx-3hp4 |
| Go | github.com/mattermost/mattermost-server | >= 11.3.0-rc1, < 11.3.3 | 11.3.3 | GHSA-mh4x-rmrx-3hp4 |
| Go | github.com/mattermost/mattermost-server | >= 10.11.0-rc1+incompatible, < 10.11.13+incompatible · >= 11.3.0-rc1+incompatible, < 11.3.3+incompatible · >= 11.4.0-rc1+incompatible, < 11.4.3+incompatible · >= 11.5.0-rc1+incompatible, < 11.5.0+incompatible | 10.11.13+incompatible, 11.3.3+incompatible, 11.4.3+incompatible, 11.5.0+incompatible | GO-2026-5507 |
| Go | github.com/mattermost/mattermost-server/v5 | all versions | — | GO-2026-5507 |
| Go | github.com/mattermost/mattermost-server/v6 | all versions | — | GO-2026-5507 |
| Go | github.com/mattermost/mattermost/server/v8 | >= 8.0.0-20250721062209-4952acea88ce, < 8.0.0-20250723052842-4cb8d8940332 | 8.0.0-20250723052842-4cb8d8940332 | GHSA-mh4x-rmrx-3hp4 |
Advisories 1
- openSUSE-SU-2026:21483-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Jul 31, 2026
References
- MMSA-2026-00624 vendor-advisory