CVE-2026-16049

_GitLab Plugin allows cross-channel post injection and phishing via missing channel permission checks in issue API endpoints_

Published Aug 17, 2026 CVSS 3.1 · 3.9 Low EPSS < 1% KEV · Not listed
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

Remediation

Vendor Solution

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

Tracking

Sign in to view the affected projects.

Advisories

No advisories available
References
History
Type Values Removed Values Added
Metrics ssvc

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

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

Weaknesses

Sources

Status
PUBLISHED
Assigner
Mattermost
Published
Updated
Aug 17, 2026, 3:26 PM
Reserved
Jul 17, 2026, 9:46 AM
Status
Undergoing Analysis
Published
Aug 17, 2026, 3:16 PM
Modified
Aug 18, 2026, 3:04 PM