CVE-2025-12421

criticalpriority · track · 0EPSS 0.004 · 36 %ileDEEUNLRUUS

grimoire priorityP2 · Scheduled

Exploitable?

—

no known exploitation

Likely / severe?

0.42% (36th) EPSS

CVSS 9.9 · critical

Is it mine?

33 products

Check your exposure

Who says so?

6 sources

cnnvd · enisa_euvd · fstec_bdu · osv

EPSS · scored 2026-10-27

Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to to verify that the token used during the code exchange originates from the same authentication flow, which allows an authenticated user to perform account takeover via a specially crafted email address used when switching authentication methods and sending a request to the /users/login/sso/code-exchange endpoint. The vulnerability requires ExperimentalEnableAuthenticationTransfer to be enabled (default: enabled) and RequireEmailVerification to be disabled (default: disabled).

cvss

Technical severity, 0–10. One row per scoring source.

9.9

010

base score 0–10 · higher = more severe · hover a vector to decode

v3.19.9criticalAV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsecondary · FSTEC (BDU) RU

v3.19.9criticalCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsecondary · ENISA EU

v3.19.9criticalCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsecondary · responsibledisclosure@mattermost.comexploitability 3.1 · impact 6

v3.19.9criticalCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsecondary · OSV

v3.19.1criticalCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:Usecondary · CVSS-BT (t0sche)

v3.19.9criticalCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsecondary · NCSC-NL NL

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: none · Automatable: no · Technical Impact: totalcoordinatorcisa_ssvcUS

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-287USCWE-303USCWE-303USCWE-303USCWE-303US

affected products (33)

Products and version ranges known to be affected.

Mattermost Mattermost Server <10.11.5all versionscert_bundDE
Mattermost Mattermost Server <10.12.2all versionscert_bundDE
Mattermost Mattermost Server <10.5.13all versionscert_bundDE
Mattermost Mattermost Server <11.0.3all versionscert_bundDE
Mattermost Mattermost Server <11.0.4all versionscert_bundDE
Mattermost Mattermost Server <11.1.0all versionscert_bundDE
Mattermost Mattermost≤ Server <11.0.4cert_bundDE
Mattermost Mattermost≤ Server <10.11.5cert_bundDE
Mattermost Mattermost≤ Server <10.12.2cert_bundDE
Mattermost Mattermost≤ Server <10.5.13cert_bundDE
Mattermost Mattermost≤ Server <11.0.3cert_bundDE
Mattermost Mattermost≤ Server <11.1.0cert_bundDE
Mattermost Mattermost≤ 11.0.0 ≤11.0.2enisa_euvdEU
Mattermost Mattermost≤ 10.5.0 ≤10.5.12enisa_euvdEU
Mattermost Mattermost≤ 10.12.0 ≤10.12.1enisa_euvdEU
Mattermost Mattermost≤ 10.11.0 ≤10.11.4enisa_euvdEU
Mattermost Inc Mattermost10.11.0 → 10.11.4fstec_bduRU
Mattermost Inc Mattermost10.12.0 → 10.12.1fstec_bduRU
Mattermost Inc Mattermost10.5.0 → 10.5.12fstec_bduRU
Mattermost Inc Mattermost11.0.0 → 11.0.2fstec_bduRU

showing 20 of 33

advisories (4)

Vendor and ecosystem advisories describing this.

NCSC-2025-0378Kwetsbaarheden verholpen in MattermostNL2025-11-28csaf · ncsc_nlNL
Mattermost heeft kwetsbaarheden verholpen in versies 11.0.x (tot en met 11.0.3), 10.12.x (tot en met 10.12.1), 10.11.x (tot en met 10.11.4) en 10.5.x (tot en met 10.5.12).
WID-SEC-W-2025-2434Mattermost Server: Mehrere Schwachstellen ermöglichen die Umgehung von SicherheitsmaßnahmenDeutsch2025-10-28csaf · cert_bundDE
Ein entfernter, authentisierter Angreifer kann mehrere Schwachstellen im Mattermost Server ausnutzen, um Sicherheitsmaßnahmen zu umgehen und so eine Kontoübernahme durchzuführen.
GHSA-mp6x-97xj-9x62Mattermost fails to to verify the token used during code exchange2025-11-27ghsa · osvUS
Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to to verify that the token used during the code exchange originates from the same authentication flow, which allows an authenticated user to perform account takeover via a specially crafted email address used when switching authentication methods and sending a request to the /users/login/sso/code-exchange endpoint. The vulnerability requires ExperimentalEnableAuthenticationTransfer to be enabled (default: enabled) and RequireEmailVerification to be disabled (default: disabled).
GO-2025-4170Mattermost fails to to verify the token used during code exchange in github.com/mattermost/mattermost-server2025-12-15vendor · osvUS
Mattermost fails to to verify the token used during code exchange in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. (If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.) The additional affected modules and versions are: github.com/mattermost/mattermost-server from v10.5.0 before v10.5.13, from v10.11.0 before v10.11.5, from v10.12.0 before v10.12.2, from v11.0.0 before v11.0.3.

also known as (6)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu osv cert_bund ncsc_nl NVD CVE.org MITRE

published 2025-11-27modified 2026-10-19

references (5)

External citations — patches, advisories, analysis.

scry

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