CVE-2026-8823

User Manager can demote bot accounts to guest without bot-management permission

3.8 LowFix available

Mattermost versions 11.7.x <= 11.7.0, 10.11.x <= 10.11.17 fail to validate bot targets when demoting users to guests which allows a lower-privileged administrator to degrade arbitrary bot accounts via the standard demote-user API.. Mattermost Advisory ID: MMSA-2026-00669

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: High
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: Low
Availability: Low

Exploit likelihood

0.32%Up 0.1 points since Jun 23, 2026

What each source reports

CVE List Score used 3.8

User Manager can demote bot accounts to guest without bot-management permission

Record: CVE-2026-8823
CVSS 3.1: 3.8 LowCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L
Weakness: CWE-863
Updated: 2026-11-02

EUVDEUVD-2026-38276 3.8

Record: EUVD-2026-38276
CVSS 3.1: 3.8 LowCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L
Updated: 2026-11-02

GitHub AdvisoriesGHSA-xmfh-3ccg-c9fx 3.8

Mattermost has an Incorrect Authorization issue

Record: GHSA-xmfh-3ccg-c9fx
CVSS 3.1: 3.8 LowCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L
Weakness: CWE-863
Updated: 2026-11-02

NVD 3.8

Record: CVE-2026-8823
CVSS 3.1: 3.8 LowCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L
Weakness: CWE-863
Updated: 2026-11-02

OSV 3.8

User Manager can demote bot accounts to guest without bot-management permission

Record: CVE-2026-8823
CVSS 3.1: 3.8 LowCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L
Weakness: CWE-863
Updated: 2026-11-02

OSVGHSA-xmfh-3ccg-c9fx 3.8

Mattermost has an Incorrect Authorization issue

Record: GHSA-xmfh-3ccg-c9fx
CVSS 3.1: 3.8 LowCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/A:L
Weakness: CWE-863
Updated: 2026-11-02

OSVGO-2026-6547 No score

Mattermost has an Incorrect Authorization issue in github.com/mattermost/mattermost-server

Mattermost has an Incorrect Authorization issue in github.com/mattermost/mattermost-server

Record: GO-2026-6547
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`github.com/mattermost/mattermost-server` Go	11.7.0 to 11.7.0	11.7.1
`github.com/mattermost/mattermost-server` Go	10.11.0 up to 10.11.18	10.11.18
`github.com/mattermost/mattermost/server/v8` Go	before 8.0.0-20260518160100-9bd77d3fc4d2	8.0.0-20260518160100-9bd77d3fc4d2
`github.com/mattermost/mattermost-server` Go	11.7.0 up to 11.7.1	11.7.1
`github.com/mattermost/mattermost-server` Go	10.11.0+incompatible up to 10.11.18+incompatible, 11.7.0+incompatible up to 11.7.1+incompatible	10.11.18+incompatible11.7.1+incompatible
`github.com/mattermost/mattermost-server/v5` Go	All versions	None known
`github.com/mattermost/mattermost-server/v6` Go	All versions	None known

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-8823 is a low vulnerability (CVSS 3.8) in Mattermost, published June 22, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.32%, the 24th percentile. Fixed in github.com/mattermost/mattermost-server 11.7.1.

References

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