CVE-2026-0999— Authentication bypass via userID login when email and username login are disabled
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I. Basic Information for CVE-2026-0999
Vulnerability Information
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Vulnerability Title
Authentication bypass via userID login when email and username login are disabled
Source: NVD (National Vulnerability Database)
Vulnerability Description
Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to properly validate login method restrictions which allows an authenticated user to bypass SSO-only login requirements via userID-based authentication. Mattermost Advisory ID: MMSA-2025-00548
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Source: NVD (National Vulnerability Database)
Vulnerability Type
认证算法的不正确实现
Source: NVD (National Vulnerability Database)
Vulnerability Title
Mattermost 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mattermost是美国Mattermost公司的一个开源协作平台。 Mattermost 11.1.2及之前的11.1.x版本、10.11.9及之前的10.11.x版本、11.2.1及之前的11.2.x版本存在安全漏洞，该漏洞源于未正确验证登录方法限制，可能允许经过身份验证的用户通过基于用户ID的身份验证绕过仅限SSO的登录要求。
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 | 11.1.0 ~ 11.1.2 | - |
II. Public POCs for CVE-2026-0999
| # | POC Description | Source Link | Shenlong Link |
|---|
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Same Patch Batch · Mattermost · 2026-02-16 · 7 CVEs total
| CVE-2026-1046 | 7.6 HIGH | Arbitrary application execution via unvalidated server-controlled URLs in Help menu |
| CVE-2025-13821 | 5.7 MEDIUM | User profile update exposes password hash and MFA secrets |
| CVE-2025-14350 | 4.3 MEDIUM | Information disclosure via channel mentions in posts |
| CVE-2026-0997 | 4.3 MEDIUM | Mattermost Zoom Plugin channel preference API lacks authorization checks |
| CVE-2026-0998 | 4.3 MEDIUM | Mattermost Zoom Plugin allows unauthorized meeting creation and post modification via insu |
| CVE-2025-14573 | 3.8 LOW | Team Admin Bypass of Invite Permissions via allow_open_invite Field |
IV. Related Vulnerabilities
Same product: Mattermost
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CSRF Protection Bypass Allows Updating a User's Authenticati - CVE-2026-27769
Connected Workspaces: Malicious remote server can manipulate - CVE-2026-24661
Unbounded Request Body Read in MS Teams Plugin {{/changes}} - CVE-2026-21388
Unbounded Request Body Read in MS Teams Plugin {{/lifecycle}
Same vendor: Mattermost
- CVE-2026-3590
Race Condition in Guest Magic Link Authentication Allows Tok - CVE-2026-28741
CSRF Protection Bypass Allows Updating a User's Authenticati - CVE-2026-27769
Connected Workspaces: Malicious remote server can manipulate - CVE-2026-24661
Unbounded Request Body Read in MS Teams Plugin {{/changes}} - CVE-2026-21388
Unbounded Request Body Read in MS Teams Plugin {{/lifecycle}
Same weakness: CWE-303
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CoreDNS TSIG authentication bypass on encrypted DNS transpor - CVE-2026-27656
Account Takeover via Substring Matching in OpenID Connect Au - CVE-2026-32953
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MiCode FileExplorer SwiFTP Server Authentication Bypass - CVE-2019-25436
Sricam DeviceViewer 3.12.0.1 Password Change Security Bypass
V. Comments for CVE-2026-0999
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