Mattermost Plugins versions <=11.8 10.20.11 11.5.7.0 _The Mattermost GitLab plugin fails to verify channel permissions when processing API requests with a caller-supplied_ {{post_id}}_, and fails to validate the_ {{web_url}} _parameter against the configured GitLab instance, which allows an authenticated attacker to inject bot-authored messages containing arbitrary URLs into channels they do not have access to via the_ {{createIssue}} _and_ {{attachCommentToIssue}} _API endpoints._ Mattermost Advisory ID: MMSA-2026-00673
Advisories

No advisories yet.

Fixes

Solution

Update Mattermost Plugins to versions 11.9.0, 10.11.21, 11.7.6 or higher.


Workaround

No workaround given by the vendor.

References
History

Mon, 17 Aug 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

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


Mon, 17 Aug 2026 15:45:00 +0000

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

Mon, 17 Aug 2026 14:45:00 +0000

Type Values Removed Values Added
Description Mattermost Plugins versions <=11.8 10.20.11 11.5.7.0 _The Mattermost GitLab plugin fails to verify channel permissions when processing API requests with a caller-supplied_ {{post_id}}_, and fails to validate the_ {{web_url}} _parameter against the configured GitLab instance, which allows an authenticated attacker to inject bot-authored messages containing arbitrary URLs into channels they do not have access to via the_ {{createIssue}} _and_ {{attachCommentToIssue}} _API endpoints._ Mattermost Advisory ID: MMSA-2026-00673
Title _GitLab Plugin allows cross-channel post injection and phishing via missing channel permission checks in issue API endpoints_
Weaknesses CWE-862
References
Metrics cvssV3_1

{'score': 3.9, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N'}


Projects

Sign in to view the affected projects.

cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published:

Updated: 2026-08-17T15:26:18.140Z

Reserved: 2026-07-17T09:46:23.992Z

Link: CVE-2026-16049

cve-icon Vulnrichment

Updated: 2026-08-17T15:26:14.599Z

cve-icon NVD

Status : Received

Published: 2026-08-17T15:16:54.420

Modified: 2026-08-17T16:16:50.840

Link: CVE-2026-16049

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-17T16:30:06Z

Weaknesses