Description
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to validate the Host header when constructing response URLs for custom slash commands which allows an authenticated attacker to redirect slash command responses to an attacker-controlled server via a spoofed Host header.. Mattermost Advisory ID: MMSA-2026-00582
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mattermost | Mattermost | 11.5.0 – ≤ 11.5.1, 10.11.0 – ≤ 10.11.13 | 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 | < 5.3.2-0.20260325160634-e738016c5920 | 5.3.2-0.20260325160634-e738016c5920 | GHSA-vqp5-2mrp-qqxg |
| Go | github.com/mattermost/mattermost-server | >= 10.11.0+incompatible, < 10.11.14+incompatible · >= 11.5.0+incompatible, < 11.5.2+incompatible | 10.11.14+incompatible, 11.5.2+incompatible | GO-2026-5671 |
| Go | github.com/mattermost/mattermost-server/v5 | all versions | — | GO-2026-5671 |
| Go | github.com/mattermost/mattermost-server/v6 | all versions | — | GO-2026-5671 |
| Go | github.com/mattermost/mattermost/server/v8 | >= 11.5.0, < 11.5.2 | 11.5.2 | GHSA-vqp5-2mrp-qqxg |
| Go | github.com/mattermost/mattermost/server/v8 | >= 10.11.0, < 10.11.14 | 10.11.14 | GHSA-vqp5-2mrp-qqxg |
| Go | github.com/mattermost/mattermost/server/v8 | < 8.0.0-20260325160634-e738016c5920 | 8.0.0-20260325160634-e738016c5920 | GHSA-vqp5-2mrp-qqxg |
Advisories 1
- openSUSE-SU-2026:21483-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Jul 31, 2026
References
- MMSA-2026-00582 vendor-advisory