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CVE-2025-12421

CRITICALCVSS 9.9/10EPSS 0.30%

Last modified

CVE-2025-12421 is a critical-severity vulnerability rated 9.9/10 on the CVSS scale. 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).. EPSS estimates a 0.30% chance of exploitation in the next 30 days.

Description

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).

Metrics

CVSS 3.1
9.9/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

EPSS Probability
0.30%

22.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
MattermostMattermost Server>= 10.5.0, < 10.5.13
MattermostMattermost Server>= 10.11.0, < 10.11.5
MattermostMattermost Server>= 10.12.0, < 10.12.2
MattermostMattermost Server>= 11.0.0, < 11.0.3

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is CVE-2025-12421?
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).
How severe is CVE-2025-12421?
CVE-2025-12421 has a CVSS score of 9.9/10 (CRITICAL severity). The EPSS model estimates a 0.30% probability of exploitation in the next 30 days.
How do I fix CVE-2025-12421?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2025-12421?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST