Mattermost up to 10.5.12/10.11.4/10.12.1/11.0.2 Email code-exchange incorrect implementation of authentication algorithm

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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7.9$0-$5k0.00

Summaryinfo

A vulnerability identified as critical has been detected in Mattermost up to 10.5.12/10.11.4/10.12.1/11.0.2. The affected element is an unknown function of the file /users/login/sso/code-exchange of the component Email Handler. The manipulation leads to incorrect implementation of authentication algorithm. This vulnerability is listed as CVE-2025-12421. The attack may be initiated remotely. There is no available exploit. You should upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Mattermost up to 10.5.12/10.11.4/10.12.1/11.0.2. This issue affects some unknown functionality of the file /users/login/sso/code-exchange of the component Email Handler. The manipulation with an unknown input leads to a incorrect implementation of authentication algorithm vulnerability. Using CWE to declare the problem leads to CWE-303. The requirements for the product dictate the use of an established authentication algorithm, but the implementation of the algorithm is incorrect. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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).

The weakness was presented by daw10. The advisory is shared at mattermost.com. The identification of this vulnerability is CVE-2025-12421 since 10/28/2025. The exploitation is known to be easy. The attack may be initiated remotely. Technical details are known, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 278109 (Mattermost Server 10.5.x <= 10.5.12 / 10.11.x <= 10.11.4 / 10.12.x <= 10.12.1 / 11.0.x <= 11.0.2 Multiple Vulnerabilities (CVE-2025-12421, MMSA-2025-00526, CVE-2025-12756)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 10.5.13, 10.11.5, 10.12.2, 11.0.3 or 11.1.0 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (278109), EUVD (EUVD-2025-199833) and CERT Bund (WID-SEC-2025-2434). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Affected

  • Mattermost Mattermost

Productinfo

Type

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 8.1
VulDB Meta Temp Score: 7.9

VulDB Base Score: 6.3
VulDB Temp Score: 6.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 9.9
CNA Vector (Mattermost): 🔒

CVSSv2info

AVACAuCIA
💳💳💳💳💳💳
💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Incorrect implementation of authentication algorithm
CWE: CWE-303
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 278109
Nessus Name: Mattermost Server 10.5.x <= 10.5.12 / 10.11.x <= 10.11.4 / 10.12.x <= 10.12.1 / 11.0.x <= 11.0.2 Multiple Vulnerabilities (CVE-2025-12421, MMSA-2025-00526, CVE-2025-12756)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Mattermost 10.5.13/10.11.5/10.12.2/11.0.3/11.1.0

Timelineinfo

10/28/2025 CVE reserved
11/27/2025 +30 days Advisory disclosed
11/27/2025 +0 days VulDB entry created
12/11/2025 +14 days VulDB entry last update

Sourcesinfo

Advisory: mattermost.com
Researcher: daw10
Status: Confirmed

CVE: CVE-2025-12421 (🔒)
GCVE (CVE): GCVE-0-2025-12421
GCVE (VulDB): GCVE-100-333713
EUVD: 🔒
CERT Bund: WID-SEC-2025-2434 - Mattermost Server: Mehrere Schwachstellen erm&ouml;glichen die Umgehung von Sicherheitsma&szlig;nahmen

Entryinfo

Created: 11/27/2025 20:20
Updated: 12/11/2025 01:49
Changes: 11/27/2025 20:20 (65), 11/27/2025 22:13 (1), 11/28/2025 16:00 (7), 12/11/2025 01:49 (2)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Discussion

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