CVE-2026-16049

EUVD-2026-60209

17.08.2026, 15:16

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

Provider	Type	Base Score	Atk. Vector	Atk. Complexity	Priv. Required	Vector
Mattermost	CNA	4.3 MEDIUM	NETWORK	LOW	LOW	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Base Score

CVSS 3.x

EPSS Score

Percentile: Unknown

Early Detection

Affected products identified ahead of NVD analysis through intelligence sources.

Vendor	Product	Version	Source
mattermost	mattermost	𝑥 ≤ 10.20.11	CNA
mattermost	mattermost	𝑥 ≤ 11.5.7	CNA

Common Weakness Enumeration

CWE-862 - Missing Authorization
The software does not perform an authorization check when an actor attempts to access a resource or perform an action.

References

https://mattermost.com/security-updates