CVE-2026-6961
High
Description
Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 Mattermost fails to sanitize FileInfo.Name received from federated peers during shared channel file sync, which allows an attacker who controls a federated server to write files to arbitrary locations within the target server's filestore via path traversal sequences in the filename field.. Mattermost Advisory ID: MMSA-2026-00661
SeverityHigh
CVSS7.6
Exploit probability23. percentile0.3%
Product
Mattermost Server
PublishedJun 12, 2026
First seenJun 12, 2026
Weakness typeCWE-22Path traversal
How to fix
Update
- mattermost mattermost_server10.11.17, 11.5.5, 11.6.2 or later
- github.com/mattermost/mattermost-server11.6.1, 11.5.5, 10.11.17, 10.11.17+incompatible, 11.5.5+incompatible, 11.6.1+incompatible or later
- github.com/mattermost/mattermost/server/v88.0.0-20260423180926-c021eeaff8f0 or later
Vendor advisories
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mattermost mattermost_server | 10.11.0 ≤ v < 10.11.17, 11.5.0 ≤ v < 11.5.5, 11.6.0 ≤ v < 11.6.2 | 10.11.17, 11.5.5, 11.6.2 |
| github.com/mattermost/mattermost-serverGo | 11.6.0 ≤ v < 11.6.1, 11.5.0 ≤ v < 11.5.5, 10.11.0 ≤ v < 10.11.17, 10.11.0+incompatible ≤ v < 10.11.17+incompatible, 11.5.0+incompatible ≤ v < 11.5.5+incompatible, 11.6.0+incompatible ≤ v < 11.6.1+incompatible | 11.6.1, 11.5.5, 10.11.17, 10.11.17+incompatible, 11.5.5+incompatible, 11.6.1+incompatible |
| github.com/mattermost/mattermost/server/v8Go | 8.0.0-20250731163400-5b955468ea1e ≤ v < 8.0.0-20260423180926-c021eeaff8f0 | 8.0.0-20260423180926-c021eeaff8f0 |
| github.com/mattermost/mattermost-server/v5Go | No range specified | — |
| github.com/mattermost/mattermost-server/v6Go | No range specified | — |
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