CVE-2026-4265
published 2026-03-16CVE-2026-4265: Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to validate team-specific upload_file permissions which allows a guest user to…
PriorityP424medium4.3CVSS 3.1
AVNACLPRLUINSUCNILAN
EPSS
0.22%
12.4th percentile
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to validate team-specific upload_file permissions which allows a guest user to post files in channels where they lack upload_file permission via uploading files in a team where they have permission and reusing the file metadata in a POST request to a different team. Mattermost Advisory ID: MMSA-2025-00553
Affected
14 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| github.com | mattermost_mattermost-server | >= 0 < 5.3.2-0.20260107144005-c7f6efdfb035 | 5.3.2-0.20260107144005-c7f6efdfb035 |
| github.com | mattermost_mattermost-server | >= 10.11.0-rc1 < 10.11.11 | 10.11.11 |
| github.com | mattermost_mattermost-server | >= 10.11.0-rc1+incompatible < 10.11.11+incompatible | 10.11.11+incompatible |
| github.com | mattermost_mattermost-server | >= 11.2.0-rc1 < 11.2.3 | 11.2.3 |
| github.com | mattermost_mattermost-server | >= 11.2.0-rc1+incompatible < 11.2.3+incompatible | 11.2.3+incompatible |
| github.com | mattermost_mattermost-server | >= 11.3.0-rc1 < 11.3.1 | 11.3.1 |
| github.com | mattermost_mattermost-server | >= 11.3.0-rc1+incompatible < 11.3.1+incompatible | 11.3.1+incompatible |
| github.com | mattermost_mattermost_server_v8 | >= 0 < 8.0.0-20260107144005-c7f6efdfb035 | 8.0.0-20260107144005-c7f6efdfb035 |
| mattermost | mattermost | 10.11.0 – 10.11.10 | — |
| mattermost | mattermost | 11.2.0 – 11.2.2 | — |
| mattermost | mattermost | 11.3.0 – 11.3.0 | — |
| mattermost | mattermost_server | >= 10.11.0 < 10.11.11 | 10.11.11 |
| mattermost | mattermost_server | >= 11.2.0 < 11.2.3 | 11.2.3 |
| mattermost | mattermost_server | >= 11.3.0 < 11.3.1 | 11.3.1 |
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OSV
Mattermost fails to validate team-specific upload_file permissions in github.com/mattermost/mattermost-server
osv·2026-03-23
CVE-2026-4265 Mattermost fails to validate team-specific upload_file permissions in github.com/mattermost/mattermost-server
Mattermost fails to validate team-specific upload_file permissions in github.com/mattermost/mattermost-server
Mattermost fails to validate team-specific upload_file permissions 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/v5 before v5.3.2-0.20260107144005-c7f6efdfb035.
OSV
Mattermost fails to validate team-specific upload_file permissions
osv·2026-03-16
CVE-2026-4265 [MEDIUM] Mattermost fails to validate team-specific upload_file permissions
Mattermost fails to validate team-specific upload_file permissions
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to validate team-specific upload_file permissions which allows a guest user to post files in channels where they lack upload_file permission via uploading files in a team where they have permission and reusing the file metadata in a POST request to a different team. Mattermost Advisory ID: MMSA-2025-00553
GHSA
Mattermost fails to validate team-specific upload_file permissions
ghsa·2026-03-16
CVE-2026-4265 [MEDIUM] CWE-863 Mattermost fails to validate team-specific upload_file permissions
Mattermost fails to validate team-specific upload_file permissions
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to validate team-specific upload_file permissions which allows a guest user to post files in channels where they lack upload_file permission via uploading files in a team where they have permission and reusing the file metadata in a POST request to a different team. Mattermost Advisory ID: MMSA-2025-00553
No detection rules found.
No public exploits indexed.
2026-03-16
Published