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CVE-2026-9820— Mattermost schemes teams endpoint exposes private team invite IDs

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 11.7.2及之前的11.7.x版本和10.11.19及之前的10.11.x版本存在授权问题漏洞，该漏洞源于未清理scheme teams端点返回的团队对象，可能导致拥有User Manager角色的用户获取私人团队的邀请链接。

CVSS 3.8 · Low EPSS 0.26% · P16

Possible ATT&CK Techniques 1 AI

T1530 · Data from Cloud Storage

Affected Version Matrix 5

VendorProduct Version RangeStatus
Mattermost Mattermost 11.7.0≤ 11.7.2 affected
10.11.0≤ 10.11.19 affected
11.8.0 unaffected
11.7.3 unaffected
10.11.20 unaffected
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I. Basic Information for CVE-2026-9820

Vulnerability Information
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Vulnerability Title
Mattermost schemes teams endpoint exposes private team invite IDs
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 11.7.x <= 11.7.2, 10.11.x <= 10.11.19 fail to sanitize team objects returned by the scheme teams endpoint, which allows a user with the User Manager role to obtain invite links for private teams and use them to join or share access to those teams via the scheme teams API endpoint.. Mattermost Advisory ID: MMSA-2026-00671
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制缺失
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 11.7.2及之前的11.7.x版本和10.11.19及之前的10.11.x版本存在授权问题漏洞，该漏洞源于未清理scheme teams端点返回的团队对象，可能导致拥有User Manager角色的用户获取私人团队的邀请链接。
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 ~ 11.7.2 -

II. Public POCs for CVE-2026-9820

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III. Intelligence Information for CVE-2026-9820

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Same Patch Batch · Mattermost · 2026-07-13 · 10 CVEs total

CVE-2026-6850 6.5 MEDIUM Crafted message attachment causes client-side denial of service via markdown parser regex
CVE-2026-10106 6.5 MEDIUM Unauthorized users can trigger interactive post actions in private channels via action coo
CVE-2026-9571 5.9 MEDIUM Deactivated user accounts can continue to obtain valid OAuth access tokens via refresh tok
CVE-2026-9597 5.4 MEDIUM Deactivated guest accounts can authenticate via magic-link token in Mattermost REST API lo
CVE-2026-10085 5.4 MEDIUM Ordinary group/direct message member can enable group_constrained and remove all channel p
CVE-2026-9708 4.9 MEDIUM Incoming webhook user attribution via unvalidated webhook owner
CVE-2026-6541 4.3 MEDIUM Unscoped updates to other playbooks' metric configuration
CVE-2026-9824 4.3 MEDIUM Remote cluster metadata enumeration via /share-channel autocomplete
CVE-2026-10103 4.3 MEDIUM Authenticated remote cluster can modify or delete posts it does not own in Mattermost Conn

IV. Related Vulnerabilities

Same product: Mattermost
Same vendor: Mattermost
Same weakness: CWE-862

V. Comments for CVE-2026-9820

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