CVE-2025-13821
Received Received - Intake
Sensitive Data Exposure in Mattermost WebSocket Allows Credential Theft

Publication date: 2026-02-16

Last updated on: 2026-02-18

Assigner: Mattermost, Inc.

Description
Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to sanitize sensitive data in WebSocket messages which allows authenticated users to exfiltrate password hashes and MFA secrets via profile nickname updates or email verification events. Mattermost Advisory ID: MMSA-2025-00560
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Meta Information
Published
2026-02-16
Last Modified
2026-02-18
Generated
2026-06-16
AI Q&A
2026-02-16
EPSS Evaluated
2026-06-15
NVD
CVE-2025-13821
EUVD
EUVD-2025-206981
Affected Vendors & Products
Showing 3 associated CPEs
Vendor Product Version / Range
mattermost mattermost_server From 10.11.0 (inc) to 10.11.10 (exc)
mattermost mattermost_server From 11.2.0 (inc) to 11.2.2 (exc)
mattermost mattermost_server From 11.1.0 (inc) to 11.1.3 (exc)
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Exploitability
CWE
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KEV
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CWE ID Description
CWE-200 The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
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Executive Summary

This vulnerability affects certain versions of Mattermost (11.1.x up to 11.1.2, 10.11.x up to 10.11.9, and 11.2.x up to 11.2.1) where the software fails to properly sanitize sensitive data in WebSocket messages.

As a result, authenticated users can exploit this flaw to exfiltrate sensitive information such as password hashes and multi-factor authentication (MFA) secrets by using profile nickname updates or email verification events.

Impact Analysis

The vulnerability allows authenticated users to extract sensitive security information like password hashes and MFA secrets.

This can lead to unauthorized access or compromise of user accounts if attackers leverage the stolen credentials or MFA secrets.

Overall, it poses a significant risk to the confidentiality of user credentials and the security of the affected Mattermost deployment.

Compliance Impact

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Detection Guidance

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Mitigation Strategies

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