CVE-2025-49222
Mattermost Shared Channel Upload Type Validation Bypass
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- High
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- None
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Mattermost Shared Channel Upload Type Validation Bypass
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.
- Record
CVE-2025-49222- CVSS 3.1
- 6.8 Medium
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N - Weakness
- CWE-434
- Updated
- 2026-11-02
EUVDEUVD-2025-25418
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.
- Record
EUVD-2025-25418- CVSS 3.1
- 6.8 Medium
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-q453-638c-h4mr
Mattermost Fails to Validate Remote Cluster Upload Sessions
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.
- Record
GHSA-q453-638c-h4mr- CVSS 3.1
- 6.8 Medium
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N - Weakness
- CWE-434
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2025-49222- CVSS 3.1
- 6.8 Medium
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N - CVSS 3.1
- 6.8 Medium
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/I:H/A:N - Weakness
- CWE-434
- Updated
- 2026-11-02
OSV
Mattermost Shared Channel Upload Type Validation Bypass
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.
- Record
CVE-2025-49222- CVSS 3.1
- 6.8 Medium
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N - Weakness
- CWE-434
- Updated
- 2026-11-07
OSVGHSA-q453-638c-h4mr
Mattermost Fails to Validate Remote Cluster Upload Sessions
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.
- Record
GHSA-q453-638c-h4mr- CVSS 3.1
- 6.8 Medium
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N - Weakness
- CWE-434
- Updated
- 2026-11-02
OSVGO-2025-3904 No score
Mattermost Fails to Validate Remote Cluster Upload Sessions in github.com/mattermost/mattermost-server
Mattermost Fails to Validate Remote Cluster Upload Sessions in github.com/mattermost/mattermost-server.
NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions.
(If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.)
The additional affected modules and versions are: github.com/mattermost/mattermost/server/v8 before v8.0.0-20250708173752-d6b35c41f0ae5.
- Record
GO-2025-3904- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
github.com/mattermost/mattermost-serverGo |
10.8.0 to 10.8.3 | 10.8.4 |
github.com/mattermost/mattermost-serverGo |
10.5.0 to 10.5.8 | 10.5.9 |
github.com/mattermost/mattermost-serverGo |
9.11.0 to 9.11.17 | 9.11.18 |
github.com/mattermost/mattermost-serverGo |
10.9.0 to 10.9.2 | 10.9.3 |
github.com/mattermost/mattermost-serverGo |
10.10.0 to 10.10.0 | 10.10.1 |
github.com/mattermost/mattermost/server/v8Go |
before 8.0.0-20250708173752-d6b35c41f0ae5 | 8.0.0-20250708173752-d6b35c41f0ae5 |
github.com/mattermost/mattermost-server/v5Go |
through 5.39.3 | None known |
github.com/mattermost/mattermost-server/v6Go |
through 5.7.2 | None known |
github.com/mattermost/mattermost-serverGo |
10.8.0 up to 10.8.4 | 10.8.4 |
github.com/mattermost/mattermost-serverGo |
10.5.0 up to 10.5.9 | 10.5.9 |
Show 7 moreShow less
| Package | Affected | Fixed |
|---|---|---|
github.com/mattermost/mattermost-serverGo |
9.11.0 up to 9.11.18 | 9.11.18 |
github.com/mattermost/mattermost-serverGo |
10.9.0 up to 10.9.3 | 10.9.3 |
github.com/mattermost/mattermost-serverGo |
10.10.0 up to 10.10.1 | 10.10.1 |
github.com/mattermost/mattermost-serverGo |
9.11.0+incompatible up to 9.11.18+incompatible, 10.5.0+incompatible up to 10.5.9+incompatible, 10.8.0+incompatible up to 10.8.4+incompatible, 10.9.0+incompatible up to 10.9.3+incompatible, 10.10.0+incompatible up to 10.10.1+incompatible | 9.11.18+incompatible10.5.9+incompatible10.8.4+incompatible10.9.3+incompatible10.10.1+incompatible |
github.com/mattermost/mattermost-server/v5Go |
All versions | None known |
github.com/mattermost/mattermost-server/v6Go |
All versions | None known |
github.com/mattermost/mattermost/server/v8Go |
All versions | None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| facts | OSV | |
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2025-49222 is a medium vulnerability (CVSS 6.8) in Mattermost, published August 21, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.30%, the 23rd percentile. Fixed in github.com/mattermost/mattermost-server 10.8.4.