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CVE-2026-9693— Mattermost thread memberships persist after team removal, exposing private channel thread metadata on re-invite

CVSS 3.5 · Low EPSS 0.16% · P6

Possible ATT&CK Techniques 1AI

T1530 · Data from Cloud Storage

Affected Version Matrix 5

VendorProductVersion RangeStatus
MattermostMattermost10.11.0≤ 10.11.20affected
11.7.0≤ 11.7.5affected
11.9.0unaffected
10.11.21unaffected
11.7.6unaffected
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I. Basic Information for CVE-2026-9693

Vulnerability Information
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Vulnerability Title
Mattermost thread memberships persist after team removal, exposing private channel thread metadata on re-invite
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 10.11.x <= 10.11.20, 11.7.x <= 11.7.5 Mattermost fails to remove thread membership records when a user is removed from or leaves a team, which allows a previously removed user who is later re-invited to the team to view private channel thread root post content and metadata via the team threads API.. Mattermost Advisory ID: MMSA-2026-00682
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
清理环节不完整
Source: CVE Program / CVE List V5
Vulnerability Title
Mattermost 资源管理错误漏洞
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 10.11.20及之前的10.11.x版本和11.7.5及之前的11.7.x版本存在资源管理错误漏洞，该漏洞源于当用户被移除或离开团队时未删除线程成员记录，可能导致重新邀请的用户通过团队线程API查看私有频道线程根帖内容和元数据。
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

VendorProductAffected VersionsCPESubscribe
MattermostMattermost 10.11.0 ~ 10.11.20 -

II. Public POCs for CVE-2026-9693

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III. Intelligence Information for CVE-2026-9693

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

CVE-2026-98168.3 HIGHInsufficient server-side validation of board member role fields permits privilege escalati
CVE-2026-98596.5 MEDIUMMattermost Boards plugin didn’t enforce role-based authorization on board channel link all
CVE-2026-100806.5 MEDIUMBoards plugin panics on WebSocket command with non-string field types
CVE-2026-105276.3 MEDIUMBoards plugin retains Board Admin rights for users demoted to System Guest
CVE-2026-160486.3 MEDIUMChannel member roles accept out-of-scope roles
CVE-2026-160474.3 MEDIUMBoard channel linking without read channel permission validation
CVE-2026-157544.2 MEDIUMMissing per-channel team-scope check in ABAC access control policy unassign allows cross-t
CVE-2026-160443.9 LOWInsufficient validation of guest board admin privileges on archive import
CVE-2026-160493.9 LOW_GitLab Plugin allows cross-channel post injection and phishing via missing channel permis
CVE-2026-755873.6 LOWPlaintext pre-auth secret exposure via Desktop App diagnostics report
CVE-2026-160463.5 LOWMissing run-state validation on finished playbook runs
CVE-2026-160452.7 LOWDelegated OAuth tokens could revoke unrelated OAuth application authorizations

IV. Related Vulnerabilities

Same product: Mattermost
Same vendor: Mattermost
Same weakness: CWE-459

V. Comments for CVE-2026-9693

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