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CVE-2026-15754— Missing per-channel team-scope check in ABAC access control policy unassign allows cross-team policy removal

Quick assessment

Affected
Mattermost Mattermost
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Mattermost是美国Mattermost公司开源的一个开源协作平台。 Mattermost 11.7.6及之前的11.7.x版本和11.8.3及之前的11.8.x版本存在授权问题漏洞，该漏洞源于访问控制策略取消分配端点未能重新验证目标通道是否仍属于请求管理员所在团队，导致经过身份验证的团队管理员在通道被移至其他团队后，可通过策略取消分配API移除其团队外部通道的ABAC策略分配。

CVSS 4.2 · Medium EPSS 0.15% · P5

Possible ATT&CK Techniques 1 AI

T1528 · Steal Application Access Token

Affected Version Matrix 5

VendorProduct Version RangeStatus
Mattermost Mattermost 11.7.0≤ 11.7.6 affected
11.8.0≤ 11.8.3 affected
11.9.0 unaffected
11.7.7 unaffected
11.8.4 unaffected
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I. Basic Information for CVE-2026-15754

Vulnerability Information
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Vulnerability Title
Missing per-channel team-scope check in ABAC access control policy unassign allows cross-team policy removal
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 11.7.x <= 11.7.6, 11.8.x <= 11.8.3 The access control policy unassign endpoint fails to re-validate that each target channel still belongs to the requesting admin's team, which allows an authenticated team administrator to remove ABAC (attribute-based access control) policy assignments from channels outside their team via the policy unassign API after a channel has been moved to another team.. Mattermost Advisory ID: MMSA-2026-00718
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制不正确
Source: CVE Program / CVE List V5
Vulnerability Title
Mattermost 授权问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mattermost是美国Mattermost公司开源的一个开源协作平台。 Mattermost 11.7.6及之前的11.7.x版本和11.8.3及之前的11.8.x版本存在授权问题漏洞，该漏洞源于访问控制策略取消分配端点未能重新验证目标通道是否仍属于请求管理员所在团队，导致经过身份验证的团队管理员在通道被移至其他团队后，可通过策略取消分配API移除其团队外部通道的ABAC策略分配。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Mattermost Mattermost 11.7.0 ~ 11.7.6 -

II. Public POCs for CVE-2026-15754

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III. Intelligence Information for CVE-2026-15754

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Same Patch Batch · Mattermost · 2026-08-17 · 13 CVEs total

CVE-2026-9816 8.3 HIGH Insufficient server-side validation of board member role fields permits privilege escalati
CVE-2026-9859 6.5 MEDIUM Mattermost Boards plugin didn’t enforce role-based authorization on board channel link all
CVE-2026-10080 6.5 MEDIUM Boards plugin panics on WebSocket command with non-string field types
CVE-2026-10527 6.3 MEDIUM Boards plugin retains Board Admin rights for users demoted to System Guest
CVE-2026-16048 6.3 MEDIUM Channel member roles accept out-of-scope roles
CVE-2026-16047 4.3 MEDIUM Board channel linking without read channel permission validation
CVE-2026-16044 3.9 LOW Insufficient validation of guest board admin privileges on archive import
CVE-2026-16049 3.9 LOW _GitLab Plugin allows cross-channel post injection and phishing via missing channel permis
CVE-2026-75587 3.6 LOW Plaintext pre-auth secret exposure via Desktop App diagnostics report
CVE-2026-9693 3.5 LOW Mattermost thread memberships persist after team removal, exposing private channel thread
CVE-2026-16046 3.5 LOW Missing run-state validation on finished playbook runs
CVE-2026-16045 2.7 LOW Delegated OAuth tokens could revoke unrelated OAuth application authorizations

IV. Related Vulnerabilities

Same product: Mattermost
Same vendor: Mattermost
Same weakness: CWE-863

V. Comments for CVE-2026-15754

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