Is CVE-2026-6739 in the CISA KEV catalog?

No. CVE-2026-6739 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-6739?

CVE-2026-6739 has a CVSS v3 base score of 6.7 (MEDIUM).

What is the EPSS score for CVE-2026-6739?

CVE-2026-6739 has an EPSS score of 0.26% (17th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-6739?

Upgrade mattermost server to 11.6.2 or later.

CVE & CISA-KEV Catalog

CVE-2026-6739

MEDIUM

6.7

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 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

CWE-863Incorrect Authorization

How to fix

Remediation Available

mattermost serverNVD

Affected:>= 11.6.0, < 11.6.2Fixed in:11.6.2CVE-2026-6739derived 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 RequiredHigh

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityLow

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

Exploit Intelligence

0.26%probability of exploitation in 30 days

17thpercentile

Low risk: more likely to be exploited than 17% of all known CVEs.

References

Vendor Advisory1

mattermost.com

Related Vulnerabilities

Other CWE-863 (Incorrect Authorization) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2023-22518	Critical	9.8	100%	KEV + Ransom	Fix
CVE-2023-38035	Critical	9.8	100%	KEV + Ransom	-
CVE-2022-46169	Critical	9.8	100%	KEV	Fix
CVE-2025-29927	Critical	9.1	100%	-	Fix
CVE-2024-38856	Critical	9.8	99%	KEV	Fix
CVE-2020-36289	Medium	5.3	99%	-	Fix

Embed a live status badge for CVE-2026-6739

Markdown

[![CVE-2026-6739](https://tridentstack.com/cve/badge/CVE-2026-6739.svg)](https://tridentstack.com/cve/CVE-2026-6739)

HTML

<a href="https://tridentstack.com/cve/CVE-2026-6739"><img src="https://tridentstack.com/cve/badge/CVE-2026-6739.svg" alt="CVE-2026-6739"></a>

Find and fix vulnerabilities across your fleet

TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.

Start free

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.