Description
Mattermost versions 9.9.x <= 9.9.0 and 9.5.x <= 9.5.6 fail to validate the source of sync messages and only allow the correct remote IDs, which allows a malicious remote to set arbitrary RemoteId values for synced users and therefore claim that a user was synced from another remote.
Details
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:N
Affected Packages
| Software | From version | Fixed in |
|---|---|---|
| github.com/mattermost/mattermost | — | — |
| github.com/mattermost/mattermost-server | — | — |
| github.com/mattermost/mattermost-server/v5 | — | — |
| github.com/mattermost/mattermost-server/v6 | — | — |
| github.com/mattermost/mattermost/server/v8 | — | — |
| mattermost | — | — |
| mattermost-server | — | — |
References
Similar Threats
- High CVE-2026-6347
- Medium CVE-2026-2461
- High CVE-2025-13523
- Medium CVE-2025-12689
- Low CVE-2025-13324
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