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Mattermost fails to sanitize team email addresses

Moderate severity GitHub Reviewed Published Nov 27, 2025 to the GitHub Advisory Database • Updated Dec 1, 2025

Package

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

Affected versions

>= 11.0.0, < 11.0.3
>= 10.12.0, < 10.12.2
>= 10.11.0, < 10.11.5
>= 10.5.0, < 10.5.13

Patched versions

11.0.3
10.12.2
10.11.5
10.5.13
gomod github.com/mattermost/mattermost/server/v8 (Go)
< 8.0.0-20251015091448-abbf01b9db45
8.0.0-20251015091448-abbf01b9db45

Description

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 sanitize team email addresses to be visible only to Team Admins, which allows any authenticated user to view team email addresses via the GET /api/v4/channels/{channel_id}/common_teams endpoint

References

Published by the National Vulnerability Database Nov 27, 2025
Published to the GitHub Advisory Database Nov 27, 2025
Reviewed Dec 1, 2025
Last updated Dec 1, 2025

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
None
Scope
Unchanged
Confidentiality
Low
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:N/S:U/C:L/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-2025-12559

GHSA ID

GHSA-4g87-9x45-cx2h

Source code

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