High severity · published Jun 12, 2026
CVE-2026-6739
Mattermost: Delegated admins could patch protected default system roles
7.2
CVSS
0.3%
EPSS
No
On KEV
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
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
High
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 17% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MA
Mattermost · Mattermost
11.6.0 through 11.6.1; 11.5.0 through 11.5.4; 10.11.0 through 10.11.15; 10.11.0 through 10.11.16 · source: vendor
MS
Mattermost Server · Mattermost
10.11.0 before 10.11.17; 11.5.0 before 11.5.5; 11.6.0 before 11.6.2 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-6739
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-6739
Vendor Advisory
https://mattermost.com/security-updates
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