Sensitive Data Exposure in Mattermost WebSocket Messages
CVE-2025-13821

5.7MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
16 February 2026

What is CVE-2025-13821?

Certain versions of Mattermost fail to properly sanitize sensitive data during WebSocket communications, which can lead to compromised user credentials. Authenticated users may exploit this vulnerability by manipulating profile nicknames or email verifications to extract password hashes and multifactor authentication secrets. These security shortcomings can have severe implications for user account integrity and overall system security.

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Affected Version(s)

Mattermost 11.1.0 <= 11.1.2

Mattermost 10.11.0 <= 10.11.9

Mattermost 11.2.0 <= 11.2.1

References

https://mattermost.com/security-updates
vendor-advisory

CVSS V3.1

Score:
5.7
Severity:
MEDIUM
Confidentiality:
High
Integrity:
None
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
Required
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

daw10
JSON
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