Vulnerability · Published Nov 13, 2025 · Assigned by Mattermost
CVE-2025-11777Cross-team channel membership access
Low 3.1
In plain English
A low-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 9% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)3.1Low
Exploit odds (30 days)0.2%top 90.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
Mattermost versions 10.11.x <= 10.11.3, 10.5.x <= 10.5.11 fail to properly validate team membership permissions in the Add Channel Member API which allows users from one team to access user metadata and channel membership information from other teams via the API endpoint
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/mattermost/mattermost | 5.3.2-0.20250905150616-ba86dfc5876b | GHSA-mqcj-8c2g-h97q |
| Go | github.com/mattermost/mattermost | no fix listed | GO-2025-4122 |
| Go | github.com/mattermost/mattermost-server | 10.11.4+incompatible, 10.5.12+incompatible | GO-2025-4122 |
| Go | github.com/mattermost/mattermost-server | 5.3.2-0.20250905150616-ba86dfc5876b | GHSA-mqcj-8c2g-h97q |
| Go | github.com/mattermost/mattermost-server | 10.5.12 | GHSA-mqcj-8c2g-h97q |
| Go | github.com/mattermost/mattermost-server | 10.11.4 | GHSA-mqcj-8c2g-h97q |
| Go | github.com/mattermost/mattermost-server/v5 | no fix listed | GO-2025-4122 |
| Go | github.com/mattermost/mattermost-server/v5 | 5.3.2-0.20250905150616-ba86dfc5876b | GHSA-mqcj-8c2g-h97q |
| Go | github.com/mattermost/mattermost-server/v6 | 5.3.2-0.20250905150616-ba86dfc5876b | GHSA-mqcj-8c2g-h97q |
| Go | github.com/mattermost/mattermost-server/v6 | no fix listed | GO-2025-4122 |
| Go | github.com/mattermost/mattermost/server/v8 | 8.0.0-20250905150616-ba86dfc5876b | GHSA-mqcj-8c2g-h97q |
| Go | github.com/mattermost/mattermost/server/v8 | 8.0.0-20251212204551-54f2e9b4afd5 | GO-2025-4122 |
| Go | github.com/mattermost/mattermost/v5 | no fix listed | GO-2025-4122 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mattermost | Mattermost | 10.11.0 – through 10.11.310.5.0 – through 10.5.11 |
Weakness: CWE-863 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N