CVE-2026-19541
Received Received - Intake

Outgoing OAuth Client Secret Exposure in Mattermost

Publication date: 2026-10-16

Last updated on: 2026-10-16

Assigner: Mattermost, Inc.

Description
Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to require re-entry of the stored client secret when validating an outgoing OAuth connection, which allows an authenticated user with permission to manage outgoing OAuth connections to obtain the secret via pointing the token URL at an attacker-controlled endpoint and triggering validation.. Mattermost Advisory ID: MMSA-2026-00761

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Meta Information

Published
2026-10-16
Last Modified
2026-10-16
Generated
2026-10-16
AI Q&A
2026-10-16
EPSS Evaluated
N/A
NVD
CVE-2026-19541
EUVD
EUVD-2026-102805

Affected Vendors & Products

Showing 4 associated CPEs
Vendor Product Version / Range
Mattermost Mattermost 11.9.0
Mattermost Mattermost 11.8.0
Mattermost Mattermost 11.7.0
Mattermost Mattermost 11.10.0

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-201 The code transmits data to another actor, but a portion of the data includes sensitive information that should not be accessible to that actor.

Attack-Flow Graph

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Executive Summary

Mattermost versions between 11.7.0 and 11.10.1 fail to require re-entry of the stored client secret when validating an outgoing OAuth connection. This allows an authenticated user with permission to manage outgoing OAuth connections to obtain the secret by redirecting the token URL to an attacker-controlled endpoint and triggering validation.

Impact Analysis

An attacker could gain access to the OAuth client secret, potentially allowing them to impersonate the application, access user data, or perform actions on behalf of users if the secret is reused elsewhere.

Compliance Impact

This vulnerability could lead to unauthorized access to sensitive data, violating confidentiality requirements under GDPR and HIPAA. Organizations may face compliance violations, fines, or reputational damage if user data is exposed due to this issue.

Mitigation Strategies

Update Mattermost to a version that fixes the vulnerability. Specifically, upgrade to versions 11.9.2, 11.8.6, 11.7.11, or 11.10.2 or later to address the issue.

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