Vulnerability · Published Sep 15, 2025 · Assigned by Mattermost
CVE-2025-9076Mattermost Server exposes sensitive user credentials during shared channel membership synchronization
Medium 6.5
In plain English
A medium-severity missing 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 0.3% (higher than 18% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Mattermost versions 10.10.x <= 10.10.1 fail to properly sanitize user data during shared channel membership synchronization, which allows malicious or compromised remote clusters to access sensitive user information via unsanitized user objects. This vulnerability affects Mattermost Server instances with shared channels enabled.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | 10.10.2 | GHSA-3vcm-c42p-3hhf |
| Go | github.com/mattermost/mattermost-server | 10.10.2+incompatible | GO-2025-3950 |
| Go | github.com/mattermost/mattermost-server/v5 | no fix listed | GO-2025-3950 |
| Go | github.com/mattermost/mattermost-server/v6 | no fix listed | GO-2025-3950 |
| Go | github.com/mattermost/mattermost/server/v8 | 8.0.0-20250729073403-517ae758cd02 | GHSA-3vcm-c42p-3hhf |
| Go | github.com/mattermost/mattermost/server/v8 | no fix listed | GO-2025-3950 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mattermost | Mattermost | 10.10.0 – through 10.10.1 |
Weakness: CWE-862 · Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N