Description
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly handle very long passwords, which allows an attacker to overload the server CPU and memory via executing login attempts with multi-megabyte passwords. Mattermost Advisory ID: MMSA-2026-00587
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mattermost | Mattermost | 11.3.0 – ≤ 11.3.0, 11.2.0 – ≤ 11.2.2, 10.11.0 – ≤ 10.11.10 | 11.4.0 |
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 |
| openSUSE Leap 15.6 | govulncheck-vulndb | 0.0.20260326T203309-150000.1.155.2 | SUSE-SU-2026:1135-1 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | < 5.3.2-0.20260129164748-7201f42d955f | 5.3.2-0.20260129164748-7201f42d955f | GHSA-m5rv-56xx-hfc6 |
| Go | github.com/mattermost/mattermost-server | >= 10.11.0-rc1, < 10.11.11 | 10.11.11 | GHSA-m5rv-56xx-hfc6 |
| Go | github.com/mattermost/mattermost-server | >= 11.2.0-rc1, < 11.2.3 | 11.2.3 | GHSA-m5rv-56xx-hfc6 |
| Go | github.com/mattermost/mattermost-server | >= 11.3.0-rc1, < 11.3.1 | 11.3.1 | GHSA-m5rv-56xx-hfc6 |
| Go | github.com/mattermost/mattermost-server | >= 10.11.0-rc1+incompatible, < 10.11.11+incompatible · >= 11.2.0-rc1+incompatible, < 11.2.3+incompatible · >= 11.3.0-rc1+incompatible, < 11.3.1+incompatible | 10.11.11+incompatible, 11.2.3+incompatible, 11.3.1+incompatible | GO-2026-4731 |
| Go | github.com/mattermost/mattermost-server/v5 | all versions | — | GO-2026-4731 |
| Go | github.com/mattermost/mattermost-server/v6 | all versions | — | GO-2026-4731 |
| Go | github.com/mattermost/mattermost/server/v8 | < 8.0.0-20260129164748-7201f42d955f | 8.0.0-20260129164748-7201f42d955f | GHSA-m5rv-56xx-hfc6 |
Advisories 3
- openSUSE-SU-2026:21483-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Jul 31, 2026
- SUSE-SU-2026:1135-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Mar 31, 2026
- WID-SEC-2026-0422 Mattermost: Mehrere Schwachstellen BSI CERT-Bund (WID) · Mar 19, 2026
References
- MMSA-2026-00587 vendor-advisory