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CVE-2026-18223— Mattermost invitation tokens not bound to invited email address allowing unauthorized team and private channel access

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 版本 11.10.x（≤ 11.10.0）、11.7.x（≤ 11.7.9）、11.9.x（≤ 11.9.1）和 11.8.x（≤ 11.8.5）在兑换团队和访客邀请令牌时，未能对受邀收件人的电子邮件地址进行验证。这导致已认证的攻击者可以通过被转发或泄露的邀请链接加入团队，或未经授权访问私有频道。Mattermost 安全公告编号：MMSA-2026-00747。

CVSS 5.0 · Medium EPSS 0.16% · P5

Affected Version Matrix 9

VendorProduct Version RangeStatus
Mattermost Mattermost 11.10.0≤ 11.10.0 affected
11.7.0≤ 11.7.9 affected
11.9.0≤ 11.9.1 affected
11.8.0≤ 11.8.5 affected
11.11.0 unaffected
11.10.1 unaffected
11.7.10 unaffected
11.9.2 unaffected
… +1 more rows
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I. Basic Information for CVE-2026-18223

Vulnerability Information
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Vulnerability Title
Mattermost invitation tokens not bound to invited email address allowing unauthorized team and private channel access
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to validate the invited recipient's email address when redeeming team and guest invitation tokens, which allows an authenticated attacker to join a team or gain unauthorized access to private channels via a forwarded or leaked invitation link.. Mattermost Advisory ID: MMSA-2026-00747
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制不正确
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Mattermost Mattermost 11.10.0 ~ 11.10.0 -

II. Public POCs for CVE-2026-18223

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III. Intelligence Information for CVE-2026-18223

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Same Patch Batch · Mattermost · 2026-10-16 · 15 CVEs total

CVE-2026-16453 7.1 HIGH Mattermost SAML RelayState forgery allows unauthorized team membership
CVE-2026-19541 6.5 MEDIUM Outgoing OAuth connection client secret exposure during connection validation
CVE-2026-18551 6.5 MEDIUM Mattermost guest account privilege escalation via member roles API
CVE-2026-19621 6.5 MEDIUM Mattermost leaks interactive-message integration secrets to non-admin users via post-delet
CVE-2026-16251 6.5 MEDIUM Mattermost local image proxy allows server memory exhaustion via unbounded image response
CVE-2026-18795 6.4 MEDIUM Missing server side validation allowed user to quarantine a DM and GM post
CVE-2026-19601 4.9 MEDIUM Disclosure of AD/LDAP bind password via Test Connection
CVE-2026-19600 4.5 MEDIUM Mattermost logs plaintext authentication tokens in debug-level server logs on failed auth
CVE-2026-19076 4.4 MEDIUM Mattermost fails to reject OAuth application sessions in account type switch, allowing acc
CVE-2026-19603 4.3 MEDIUM Private channel ID disclosure via user status endpoints
CVE-2026-19867 4.3 MEDIUM Uncapped mention keys in user notification properties allow CPU exhaustion during post pro
CVE-2026-18560 4.3 MEDIUM Improper order of authorisations in Mattermost GetFile API leads to an authenticated user
CVE-2026-18256 4.3 MEDIUM Private team metadata disclosure via the team search API
CVE-2026-18799 4.3 MEDIUM Mattermost Server fails to restrict Slack import account binding, allowing team admins to

IV. Related Vulnerabilities

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

V. Comments for CVE-2026-18223

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