CVE-2026-6739Network attack vector

Privilege escalation via default-role permission bypass

Published Jun 12, 2026 · Updated Jun 12, 2026

Incorrect authorization in Mattermost allows remote authenticated users with delegated user management to escalate privileges via the role API. The patchRole handler omitted system_user and system_guest from its protected-role list and changed their permissions without checking PermissionManageSystem. Affected versions are 10.11.0 through 10.11.16, 11.5.0 through 11.5.4, and 11.6.0 through 11.6.1; control is limited to built-in role permissions.

CVSS severity6.7
Medium
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect authorization in Mattermost allows remote authenticated users with delegated user management to escalate privileges via the role API. The patchRole handler omitted system_user and system_guest from its protected-role list and changed their permissions without checking PermissionManageSystem. Affected versions are 10.11.0 through 10.11.16, 11.5.0 through 11.5.4, and 11.6.0 through 11.6.1; control is limited to built-in role permissions.

The record

CVE
CVE-2026-6739
Published
Jun 12, 2026
Updated
Jun 12, 2026
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-863, T1068
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 12, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 12, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.11.0 <=10.11.15
  2. Affected versionversion=10.11.0 <=10.11.16
  3. Affected versionversion=11.5.0 <=11.5.4
  4. Affected versionversion=11.6.0 <=11.6.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mattermost · Mattermostversion=10.11.0 <=10.11.15; version=10.11.0 <=10.11.16; version=11.5.0 <=11.5.4; version=11.6.0 <=11.6.1

Published CVSS scores

7.2NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
6.7Mattermost, Inc.CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-863Incorrect Authorization
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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