Mattermost ABAC parent policy bypass via policy update endpoint

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-82920
StatePUBLISHED
AssignerMattermost
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-14 14:17:13 UTC
Updated2026-09-14 20:16:57 UTC
DescriptionMattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7 fail to enforce authorization boundaries on the access control policy update endpoint which allows a channel or team administrator to detach a system-assigned ABAC parent policy via a crafted PUT /api/v4/access_control_policies request with an empty imports list.. Mattermost Advisory ID: MMSA-2026-00724

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

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

Problem Types: CWE-863 | CWE-863 CWE-863: Incorrect Authorization

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N
3.1CNACVSS5.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
High
User Interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mattermost Mattermost affected 11.9.0 11.9.0 semver Not specified
CNA Mattermost Mattermost affected 11.8.0 11.8.4 semver Not specified
CNA Mattermost Mattermost affected 11.7.0 11.7.7 semver Not specified
CNA Mattermost Mattermost unaffected 11.10.0 Not specified
CNA Mattermost Mattermost unaffected 11.9.1 Not specified
CNA Mattermost Mattermost unaffected 11.8.5 Not specified
CNA Mattermost Mattermost unaffected 11.7.8 Not specified

References

ReferenceSourceLinkTags
mattermost.com/security-updates [email protected] mattermost.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: kiwi_71 (en)

Additional Advisory Data

Solutions

CNA: Update Mattermost to versions 11.10.0, 11.9.1, 11.8.5, 11.7.8 or higher.

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