Description
Mattermost versions 10.11.x <= 10.11.8 fail to validate input size before processing hashtags which allows an authenticated attacker to exhaust CPU resources via a single HTTP request containing a post with thousands space-separated tokens
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mattermost | Mattermost | 10.11.0 – ≤ 10.11.8 | 11.2.0 |
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 | 0.0.20260226T182644-150000.1.149.1 | SUSE-SU-2026:0757-1 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | >= 10.11.0, < 10.11.9 | 10.11.9 | GHSA-9r42-rhw3-2222 |
| Go | github.com/mattermost/mattermost-server | >= 11.0.0, < 11.2.0 | 11.2.0 | GHSA-9r42-rhw3-2222 |
| Go | github.com/mattermost/mattermost-server | >= 10.11.0+incompatible, < 10.11.9+incompatible · >= 11.0.1+incompatible, < 11.2.0+incompatible | 10.11.9+incompatible, 11.2.0+incompatible | GO-2026-4325 |
Advisories 3
- openSUSE-SU-2026:21483-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Jul 31, 2026
- SUSE-SU-2026:0757-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Mar 4, 2026
- WID-SEC-2025-2880 Mattermost Server und Desktop: Mehrere Schwachstellen BSI CERT-Bund (WID) · Feb 26, 2026