Skip to content

Mattermost fails to sanitize sensitive data in WebSocket messages

Moderate severity GitHub Reviewed Published Feb 16, 2026 to the GitHub Advisory Database • Updated Feb 19, 2026

Package

gomod github.com/mattermost/mattermost-server (Go)

Affected versions

>= 11.1.0, < 11.1.3
>= 10.11.0, < 10.11.10
>= 11.2.0, < 11.2.2
< 5.3.2-0.20251210191531-cd17b61de41b

Patched versions

5.3.2-0.20251210191531-cd17b61de41b
gomod github.com/mattermost/mattermost/server/v8 (Go)
< 8.0.0-20251210191531-cd17b61de41b
8.0.0-20251210191531-cd17b61de41b

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

References

Published by the National Vulnerability Database Feb 16, 2026
Published to the GitHub Advisory Database Feb 16, 2026
Reviewed Feb 19, 2026
Last updated Feb 19, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(9th percentile)

Weaknesses

Exposure of Sensitive Information to an Unauthorized Actor

The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. Learn more on MITRE.

CVE ID

CVE-2025-13821

GHSA ID

GHSA-pp9j-pf5c-659x

Source code

Loading Checking history
See something to contribute? Suggest improvements for this vulnerability.