CVE-2026-16047

🔶 medium

Summary

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing, or bulk-creating boards with an arbitrary channelId. Mattermost Advisory ID: MMSA-2026-00674

CVSS Score

4.3

Medium

EPSS Score

0.2

Exploit Probability

Published Date

2026-08-17

First Seen: 2026-08-18

📊 Relative Risk Intelligence

This CVE is Lower Risk - more severe than 5.3% of all 348,695 vulnerabilities in our database.

#330,067

Below average severity

Severity Percentile

🎯 CISA SSVC Assessment Updated: Aug 17, 2026

🔍 Exploitation Status

None

No known exploits

⚙️ Automatable

Requires human interaction

💥 Technical Impact

Partial

Limited system impact

🏆 Discovered By

GuyNesher

SSVC data provided by CISA

Last Modified 2026-08-18

Source NVD 🔗

CVSS Vector 3.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

CWE IDs (Weakness Types)

CWE-862

📦 Affected Products 3

Vendor	Product	Status	Affected Versions
mattermost	mattermost_server	Affected	> 10.11.0 < 10.11.22
mattermost	mattermost_server	Affected	> 11.7.0 < 11.7.7
mattermost	mattermost_server	Affected	> 11.8.0 < 11.8.4

🔗 References 1

https://mattermost.com/security-updates

Vendor Advisory

🔗 Related CVEs 6

CVE ID	Severity	CVSS	EPSS	Summary	Published
CVE-2026-10527	🔶 medium	6.3	0.2	Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fails to reconcile SchemeAdmin flags with a ...	2026-08-17
CVE-2026-15754	🔶 medium	4.2	0.2	Mattermost versions 11.7.x <= 11.7.6, 11.8.x <= 11.8.3 The access control policy unassign endpoint fails to re-validate ...	2026-08-17
CVE-2026-16044	🔶 medium	5.4	0.2	Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21 fail to prevent guest users from receiving Board Admin privile...	2026-08-17
CVE-2026-16045	🔶 medium	4.3	0.2	Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21 Mattermost failed to restrict OAuth deauthorization and person...	2026-08-17
CVE-2026-16046	🔶 medium	4.3	0.2	Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21 fail to enforce run-state validation on write operations for f...	2026-08-17
CVE-2026-16048	🔶 medium	6.3	0.2	Mattermost versions 11.8.x <= 11.8.2, 11.7.x <= 11.7.6, 10.11.x <= 10.11.21 fail to restrict channel member role assignm...	2026-08-17

These CVEs affect the same products