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Vulnerabilities

Vulnerability · 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 s

Published Nov 27, 2025 · catalog updated Feb 26, 2026 · Mattermost Mattermost

Last checked Oct 26, 2026. A connected source was read within the last 7 days.

Check this week

CVE-2025-12421 is not in CISA KEV. FIRST estimates a 42.00% chance of exploitation in the next 30 days. Check whether you run Mattermost Mattermost.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Critical9.9
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
42.00%
Remediation
Advisory link
Affected products
vendor Mattermost Mattermost 10.12.0 ≤10.12.1

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).

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor Mattermost Mattermost 10.12.0 ≤10.12.110.12.0 ≤10.12.1

How to fix CVE-2025-12421

  • No stored fix

    No vendor fix text is stored. Use the linked advisory before you change production.

  • Version check

    Seen in 10.12.0 ≤10.12.1

  • Official advisories

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2025-12421 is not in CISA KEV. FIRST estimates a 42.00% chance of exploitation in the next 30 days. Check whether you run Mattermost Mattermost.

Which versions are affected?

Compare what you have installed with Mattermost Mattermost 10.12.0 ≤10.12.1 10.12.0 ≤10.12.1. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 42.00%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Nov 27, 2025 · EUVD

    Detected

    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-

  2. Feb 26, 2026 · EUVD

    Updated

    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-

Sources

  • EUVDVulnerability recordEUVD-2025-199833

    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 specia

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Feb 26, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • EUVDOct 26, 2026