Vulnerability

CVE-2026-6739

Medium· 6.7CVSS6.7

.rules3/5

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 require system-level permission when patching protected default system roles, which allows authenticated users with delegated user-management permissions to escalate privileges by altering built-in role permissions via the role patch API.. Mattermost Advisory ID: MMSA-2026-00656

Threat signal

67/100

Elevated

Severity

medium

CVSS

6.7

EPSS

—

Active

CVSS

v3.1via NVDOpen in FIRST calculator →

6.7/ 10MEDIUMCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L

Attack VectorNetworkExploitable remotely over the internet — no local access needed.
Attack ComplexityLowNo special conditions — exploit works reliably.
Privileges RequiredHighAdmin / root privileges required.
User InteractionNoneFully automated — no victim action needed.
ScopeUnchangedImpact contained to the vulnerable component.
Confidentiality ImpactHighTotal disclosure of sensitive data.
Integrity ImpactHighTotal compromise of integrity — full data modification possible.
Availability ImpactLowReduced performance / interruptions.

EPSS

No EPSS data

FIRST.org publishes EPSS daily. Coverage isn't universal — pre-disclosure CVEs and reserved IDs don't carry an EPSS score until at least one exploitation signal lands. Score will appear within 24 hours of the next EPSS pull.

Vendor VEX

No VEX statements published for CVE-2026-6739. Vendors publish VEX (Vulnerability Exploitability eXchange) to assert per-product whether a CVE is actually exploitable in their distribution.

SSVCDefer

No exploitation, limited impact or prevalence

exploitation: none
automatable: no
impact: partial
mission: support

Lifecycle

2026-06-12Published
2026-06-12Last modified1 source

References

https://mattermost.com/security-updates

No source-event history recorded yet. New revisions will appear here as ingestors re-fetch this CVE.