Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to apply the internal-connection filter to OAuth endpoint requests, which allows a System Administrator to make the server issue requests to internal network addresses and read the responses via the configured OAuth token and userinfo endpoints.. Mattermost Advisory ID: MMSA-2026-00776
Advisories

No advisories yet.

Fixes

Solution

Update Mattermost to versions 11.11.0, 11.9.2, 11.8.6, 11.7.11, 11.10.2 or higher.


Workaround

No workaround given by the vendor.

References
History

Wed, 07 Oct 2026 17:00:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost mattermost Server
CPEs cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
Vendors & Products Mattermost mattermost Server

Wed, 23 Sep 2026 14:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Tue, 22 Sep 2026 21:45:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost

Tue, 22 Sep 2026 20:45:00 +0000

Type Values Removed Values Added
Description Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to apply the internal-connection filter to OAuth endpoint requests, which allows a System Administrator to make the server issue requests to internal network addresses and read the responses via the configured OAuth token and userinfo endpoints.. Mattermost Advisory ID: MMSA-2026-00776
Title Mattermost server-side request forgery via OAuth endpoints configurable by a System Administrator
Weaknesses CWE-918
References
Metrics cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published:

Updated: 2026-09-23T13:10:47.754Z

Reserved: 2026-09-22T19:59:57.887Z

Link: CVE-2026-96259

cve-icon Vulnrichment

Updated: 2026-09-23T13:10:41.631Z

cve-icon NVD

Status : Analyzed

Published: 2026-09-22T21:17:34.910

Modified: 2026-10-07T16:41:14.847

Link: CVE-2026-96259

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-22T21:30:20Z

Weaknesses