Description
Mattermost versions 11.6.x <= 11.6.5, 10.11.x <= 10.11.20, 11.8.x <= 11.8.1, 11.7.x <= 11.7.4 fail to limit the number of frames and enforce the file size cap on animated GIF uploads, which allows an authenticated attacker to cause a denial of service via a crafted animated GIF uploaded as a custom emoji.. Mattermost Advisory ID: MMSA-2026-00695
Published: 2026-07-27
Score: 6.5 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Analysis and contextual insights are available on OpenCVE Cloud.

Remediation

Vendor Solution

Update Mattermost to versions 11.9.0, 11.6.6, 10.11.21, 11.8.2, 11.7.5 or higher.

Tracking

Sign in to view the affected projects.

Advisories

No advisories yet.

References
Link Providers
https://mattermost.com/security-updates cve-icon
History

Mon, 27 Jul 2026 15:45:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost

Mon, 27 Jul 2026 15:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

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

Mon, 27 Jul 2026 14:30:00 +0000

Type Values Removed Values Added
Description Mattermost versions 11.6.x <= 11.6.5, 10.11.x <= 10.11.20, 11.8.x <= 11.8.1, 11.7.x <= 11.7.4 fail to limit the number of frames and enforce the file size cap on animated GIF uploads, which allows an authenticated attacker to cause a denial of service via a crafted animated GIF uploaded as a custom emoji.. Mattermost Advisory ID: MMSA-2026-00695
Title Mattermost Server Denial of Service via Animated GIF Emoji Upload
Weaknesses CWE-409
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'}

Subscriptions

Mattermost Mattermost
cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published:

Updated: 2026-07-27T15:05:28.394Z

Reserved: 2026-06-04T07:34:33.428Z

Link: CVE-2026-10819

cve-icon Vulnrichment

Updated: 2026-07-27T15:05:23.347Z

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-07-27T15:22:43Z

Weaknesses