CVE-2026-5755

Denial of service via crafted TIFF file upload

Published May 22, 2026 CVSS 3.1 · 6.5 Medium EPSS < 1% KEV · Not listed
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

Remediation

Vendor Solution

Update Mattermost to versions 11.7.0, 11.6.1, 11.5.3, 11.5.4, 11.4.5, 10.11.15 or higher.

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-37j2-3vv8-cf24 Mattermost doesn't validate the TIFF IFD offset in the image header before allocating memory
References
History
Type Values Removed Values Added
First Time appeared Mattermost mattermost Server
CPEs cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
Vendors & Products Mattermost mattermost Server
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost
Type Values Removed Values Added
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
Title Denial of service via crafted TIFF file upload
Weaknesses CWE-400
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
Mattermost
Published
Updated
May 22, 2026, 12:15 PM
Reserved
Apr 7, 2026, 4:22 PM
Status
Analyzed
Published
May 22, 2026, 11:16 AM
Modified
Jul 23, 2026, 4:10 PM