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Mattermost Fails to Validate Remote Cluster Upload Sessions

Moderate severity GitHub Reviewed Published Aug 21, 2025 to the GitHub Advisory Database • Updated Aug 29, 2025

Package

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

Affected versions

>= 10.8.0, <= 10.8.3
>= 10.5.0, <= 10.5.8
>= 9.11.0, <= 9.11.17
>= 10.9.0, <= 10.9.2
= 10.10.0

Patched versions

10.8.4
10.5.9
9.11.18
10.9.3
10.10.1
gomod github.com/mattermost/mattermost-server/v5 (Go)
<= 5.39.3
None
gomod github.com/mattermost/mattermost-server/v6 (Go)
<= 5.7.2
None
gomod github.com/mattermost/mattermost/server/v8 (Go)
< 8.0.0-20250708173752-d6b35c41f0ae5
8.0.0-20250708173752-d6b35c41f0ae5

Description

Mattermost versions 10.8.x <= 10.8.3, 10.5.x <= 10.5.8, 9.11.x <= 9.11.17, 10.9.x <= 10.9.2, 10.10.x <= 10.10.0 fail to validate upload types in remote cluster upload sessions which allows a system admin to upload non-attachment file types via shared channels that could potentially be placed in arbitrary filesystem directories.

References

Published by the National Vulnerability Database Aug 21, 2025
Published to the GitHub Advisory Database Aug 21, 2025
Reviewed Aug 21, 2025
Last updated Aug 29, 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
High
User interaction
None
Scope
Changed
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:H/UI:N/S:C/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.
(10th percentile)

Weaknesses

Unrestricted Upload of File with Dangerous Type

The product allows the attacker to upload or transfer files of dangerous types that can be automatically processed within the product's environment. Learn more on MITRE.

CVE ID

CVE-2025-49222

GHSA ID

GHSA-q453-638c-h4mr

Source code

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