CVE-2026-5755
Medium
Description
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.2, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate the TIFF IFD offset in the image header before allocating memory, which allows authenticated users with file upload or posting permissions to cause a denial of service (server OOM) via uploading a crafted TIFF file or posting a URL that serves one.. Mattermost Advisory ID: MMSA-2026-00648
SeverityMedium
CVSS6.5
Exploit probability—
Product
Mattermost Server
PublishedMay 22, 2026
First seenMay 22, 2026
Weakness typeCWE-400Uncontrolled resource consumption
How to fix
Update
- mattermost mattermost_server10.11.15, 11.4.5, 11.5.3, 11.6.1 or later
- github.com/mattermost/mattermost-server11.6.1, 11.5.4, 11.4.5, 10.11.15, 10.11.15+incompatible, 11.4.5+incompatible, 11.5.4+incompatible, 11.6.1+incompatible or later
Vendor advisories
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mattermost mattermost_server | 10.11.0 ≤ v < 10.11.15, 11.4.0 ≤ v < 11.4.5, 11.5.0 ≤ v < 11.5.3, 11.6.0 ≤ v < 11.6.1 | 10.11.15, 11.4.5, 11.5.3, 11.6.1 |
| github.com/mattermost/mattermost-serverGo | 11.6.0 ≤ v < 11.6.1, 11.5.0 ≤ v < 11.5.4, 11.4.0 ≤ v < 11.4.5, 10.11.0 ≤ v < 10.11.15, 10.11.0+incompatible ≤ v < 10.11.15+incompatible, 11.4.0+incompatible ≤ v < 11.4.5+incompatible, 11.5.0+incompatible ≤ v < 11.5.4+incompatible, 11.6.0+incompatible ≤ v < 11.6.1+incompatible | 11.6.1, 11.5.4, 11.4.5, 10.11.15, 10.11.15+incompatible, 11.4.5+incompatible, 11.5.4+incompatible, 11.6.1+incompatible |
Check your version
Choose the product and enter the version you run to see whether it falls in the affected range.
In the Intelligence 360 plan
Attack Surface Management
See the assets tied to your domains, the technologies they run and known vulnerabilities in one list.