Description
An issue was discovered in Mattermost Server before 4.3.0, 4.2.1, and 4.1.2. An attacker could create fictive system-message posts via webhooks and slash commands, in the v3 or v4 REST API.
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 | 0.0.20251230T014957-150000.1.134.1 | SUSE-SU-2026:0037-1 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | < 4.1.2 | 4.1.2 | GHSA-jp57-4x34-5v94 |
| Go | github.com/mattermost/mattermost-server | >= 4.2.0-rc1, < 4.2.1 | 4.2.1 | GHSA-jp57-4x34-5v94 |
| Go | github.com/mattermost/mattermost-server | >= 4.3.0-rc1, < 4.3.0 | 4.3.0 | GHSA-jp57-4x34-5v94 |
| Go | github.com/mattermost/mattermost-server | < 4.1.2+incompatible · >= 4.2.0-rc1+incompatible, < 4.2.1+incompatible · >= 4.3.0-rc1+incompatible, < 4.3.0+incompatible | 4.1.2+incompatible, 4.2.1+incompatible, 4.3.0+incompatible | GO-2025-4201 |
Advisories 2
- openSUSE-SU-2026:21483-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Jul 31, 2026
- SUSE-SU-2026:0037-1 Security update for govulncheck-vulndb SUSE / openSUSE Security Updates · Mar 23, 2026