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CVE-2026-9571— Deactivated user accounts can continue to obtain valid OAuth access tokens via refresh token grant in Mattermost

CVSS 5.9 · Medium EPSS 0.17% · P7

Possible ATT&CK Techniques 1AI

T1528 · Steal Application Access Token

Affected Version Matrix 7

VendorProductVersion RangeStatus
MattermostMattermost11.7.0≤ 11.7.2affected
11.6.0≤ 11.6.4affected
10.11.0≤ 10.11.19affected
11.8.0unaffected
11.7.3unaffected
11.6.5unaffected
10.11.20unaffected
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I. Basic Information for CVE-2026-9571

Vulnerability Information
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Vulnerability Title
Deactivated user accounts can continue to obtain valid OAuth access tokens via refresh token grant in Mattermost
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to invalidate OAuth refresh tokens upon user account deactivation, which allows a deactivated user or an attacker in possession of a valid refresh token to obtain new functional access tokens via the OAuth refresh token grant endpoint.. Mattermost Advisory ID: MMSA-2026-00680
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
使用基本弱点进行的认证绕过
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存在授权问题漏洞，该漏洞源于未在用户账户停用时失效OAuth刷新令牌，导致被停用的用户或持有有效刷新令牌的攻击者可通过OAuth刷新令牌授权端点获取新的功能访问令牌。以下版本受到影响：11.7.2及之前的11.7.x版本、11.6.4及之前的11.6.x版本和10.11.19及之前的10.11.x版本。
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 11.7.0 ~ 11.7.2 -

II. Public POCs for CVE-2026-9571

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III. Intelligence Information for CVE-2026-9571

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

CVE-2026-68506.5 MEDIUMCrafted message attachment causes client-side denial of service via markdown parser regex
CVE-2026-101066.5 MEDIUMUnauthorized users can trigger interactive post actions in private channels via action coo
CVE-2026-95975.4 MEDIUMDeactivated guest accounts can authenticate via magic-link token in Mattermost REST API lo
CVE-2026-100855.4 MEDIUMOrdinary group/direct message member can enable group_constrained and remove all channel p
CVE-2026-97084.9 MEDIUMIncoming webhook user attribution via unvalidated webhook owner
CVE-2026-65414.3 MEDIUMUnscoped updates to other playbooks' metric configuration
CVE-2026-98244.3 MEDIUMRemote cluster metadata enumeration via /share-channel autocomplete
CVE-2026-101034.3 MEDIUMAuthenticated remote cluster can modify or delete posts it does not own in Mattermost Conn
CVE-2026-98203.8 LOWMattermost schemes teams endpoint exposes private team invite IDs

IV. Related Vulnerabilities

Same product: Mattermost
Same vendor: Mattermost
Same weakness: CWE-305

V. Comments for CVE-2026-9571

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