Vulnerability · Published May 18, 2026 · Assigned by Mattermost
CVE-2026-28732Slash command trigger-word update allowed command hijacking
Medium 4.3
In plain English
A medium-severity incorrect authorization in Mattermost from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 4% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 Fail to enforce slash command trigger-word uniqueness during command updates which allows an authenticated team member with Manage Own Slash Commands permission to hijack and impersonate existing system or custom slash commands via editing their own slash command trigger to an already-registered trigger through the command update API. Mattermost Advisory ID: MMSA-2026-00597
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | 10.11.14+incompatible, 11.4.4+incompatible, 11.5.2+incompatible | GO-2026-5726 |
| Go | github.com/mattermost/mattermost-server | 5.3.2-0.20260306123948-f5fe8ded6b63 | GHSA-wvcv-9xpm-7mqc |
| Go | github.com/mattermost/mattermost-server/v5 | no fix listed | GO-2026-5726 |
| Go | github.com/mattermost/mattermost-server/v6 | no fix listed | GO-2026-5726 |
| Go | github.com/mattermost/mattermost/server/v8 | 11.5.2 | GHSA-wvcv-9xpm-7mqc |
| Go | github.com/mattermost/mattermost/server/v8 | 8.0.0-20260306123948-f5fe8ded6b63 | GO-2026-5726 |
| Go | github.com/mattermost/mattermost/server/v8 | 10.11.14 | GHSA-wvcv-9xpm-7mqc |
| Go | github.com/mattermost/mattermost/server/v8 | 11.4.4 | GHSA-wvcv-9xpm-7mqc |
| Go | github.com/mattermost/mattermost/server/v8 | 8.0.0-20260306123948-f5fe8ded6b63 | GHSA-wvcv-9xpm-7mqc |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mattermost | Mattermost | 11.5.0 – through 11.5.110.11.0 – through 10.11.1311.4.0 – through 11.4.3 |
Weakness: CWE-863 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
References
- MMSA-2026-00597 vendor-advisory