Is CVE-2026-6689 in the CISA KEV catalog?

No. CVE-2026-6689 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-6689?

CVE-2026-6689 has a CVSS v3 base score of 4.3 (MEDIUM).

What is the EPSS score for CVE-2026-6689?

CVE-2026-6689 has an EPSS score of 0.15% (5th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-6689?

Upgrade mattermost server to 11.6.2 or later.

CVE & CISA-KEV Catalog

CVE-2026-6689

MEDIUM

4.3

CVSS v3

NVD

Description

Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 Fail to enforce PermissionInviteUser when setting AllowOpenInvite or AllowedDomains during team creation (the check was only applied on update/patch), which allows an authenticated user holding PermissionCreateTeam but not PermissionInviteUser on the resulting team to configure invite-controlled team settings (make the team publicly joinable via open invite and/or constrain membership via allowed domains) that they are not permitted to set on an existing team via POST /api/v4/teams with allow_open_invite: true and/or a non-empty allowed_domains in the request body.. Mattermost Advisory ID: MMSA-2026-00655

CWE-862Missing Authorization

How to fix

Remediation Available

mattermost serverNVD

Affected:>= 11.6.0, < 11.6.2Fixed in:11.6.2CVE-2026-6689derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredLow

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityLow

AvailabilityNone

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

Exploit Intelligence

0.15%probability of exploitation in 30 days

5thpercentile

Low risk: more likely to be exploited than 5% of all known CVEs.

References

Vendor Advisory1

mattermost.com

Related Vulnerabilities

Other CWE-862 (Missing Authorization) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2021-39226	Critical	9.8	100%	KEV	Fix
CVE-2022-0543	Critical	10.0	100%	KEV	Fix
CVE-2021-21978	Critical	9.8	99%	-	Fix
CVE-2023-52163	High	8.8	96%	KEV	-
CVE-2022-1329	High	8.8	93%	-	-
CVE-2023-6875	Critical	9.8	90%	-	-

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-06-18.