Raw vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:HSummary
CVE-2025-12419 is a critical-severity Incorrect Implementation of Authentication Algorithm (CWE-303) vulnerability in Mattermost Mattermost Server. Its CVSS base score is 9.9 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique External Remote Services (T1133); ranked at the 27th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-15 (Development Process, Standards, and Tools) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2025-12419 is a critical authentication vulnerability in Mattermost, affecting versions 10.12.x up to and including 10.12.1, 10.11.x up to and including 10.11.4, 10.5.x up to and including 10.5.12, and 11.0.x up to and including 11.0.3. It arises from improper validation of OAuth state tokens during the OpenID Connect authentication process, linked to CWE-303 (Incorrect Implementation of Authentication and Session Management). The issue was published on 2025-11-27 and carries a CVSS v3.1 base score of 9.9 (AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H).
An authenticated attacker with team creation privileges can exploit this vulnerability to take over a target user account by manipulating authentication data during the OAuth completion flow. Successful exploitation requires specific conditions: email verification disabled (the default setting), OAuth or OpenID Connect enabled, and the attacker controlling two users in the SSO system, where one has never previously logged into Mattermost.
Mattermost has published details on mitigations and patches in their security updates, available at https://mattermost.com/security-updates. Security practitioners should review this advisory for upgrade instructions and configuration recommendations to address the flaw.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-199827
Vulnerability Data
Mattermost versions 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12, 11.0.x <= 11.0.3 fail to properly validate OAuth state tokens during OpenID Connect authentication which allows an authenticated attacker with team creation privileges to take over a user account…
more
via manipulation of authentication data during the OAuth completion flow. This requires email verification to be disabled (default: disabled), OAuth/OpenID Connect to be enabled, and the attacker to control two users in the SSO system with one of them never having logged into Mattermost.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation at post-design stages directly uncovers incorrect implementations of required authentication algorithms.
Requiring documented development processes, standards, and tools reduces the chance that an established authentication algorithm is coded incorrectly.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly require correct implementation of authentication algorithms.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Secure authentication control directly requires correct implementation of authentication algorithms.
Security testing can detect flawed authentication implementations but does not prevent them by itself.
Cryptography control addresses proper use of authentication algorithms but is broader than authentication alone.
Secure development lifecycle includes verification steps that can catch incorrect authentication implementations.
Application security requirements can specify correct authentication algorithm use but do not guarantee correct implementation.
Secure coding practices reduce the likelihood of incorrect authentication algorithm implementation.