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CVE-2026-9597— Deactivated guest accounts can authenticate via magic-link token in Mattermost REST API login endpoint

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11.6.4及之前的11.6.x版本存在授权问题漏洞，该漏洞源于在魔法链接令牌登录路径中未能验证来宾账户是否已被停用，允许已停用的来宾用户通过停用前签发的魔法链接令牌获取完全有效的会话。

CVSS 5.4 · Medium EPSS 0.23% · P13

Possible ATT&CK Techniques 1 AI

T1078 · Valid Accounts

Affected Version Matrix 5

VendorProduct Version RangeStatus
Mattermost Mattermost 11.7.0≤ 11.7.2 affected
11.6.0≤ 11.6.4 affected
11.8.0 unaffected
11.7.3 unaffected
11.6.5 unaffected
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I. Basic Information for CVE-2026-9597

Vulnerability Information
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Vulnerability Title
Deactivated guest accounts can authenticate via magic-link token in Mattermost REST API login endpoint
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4 fail to verify whether a guest account is deactivated before creating a session in the magic-link token login path, which allows a deactivated guest user to obtain a fully functional session via a magic-link token issued prior to deactivation.. Mattermost Advisory ID: MMSA-2026-00681
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/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 11.7.2及之前的11.7.x版本和11.6.4及之前的11.6.x版本存在授权问题漏洞，该漏洞源于在魔法链接令牌登录路径中未能验证来宾账户是否已被停用，允许已停用的来宾用户通过停用前签发的魔法链接令牌获取完全有效的会话。
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-2026-9597

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III. Intelligence Information for CVE-2026-9597

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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-2026-10085 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
CVE-2026-9820 3.8 LOW Mattermost 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-2026-9597

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