CVE-2026-15814 PUBLISHED

Uploading a crafted image causes excessive memory allocation in the Mattermost Server

Assigner: Mattermost
Reserved: 15.07.2026 Published: 14.09.2026 Updated: 14.09.2026

Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to limit the amount of memory allocated when decoding uploaded image files which allows an authenticated user to cause excessive server memory consumption and potential denial of service via uploading a specially crafted image as a profile picture, channel file attachment, team icon, or custom brand image. Mattermost Advisory ID: MMSA-2026-00719

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CVSS Score: 6.5

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	None
Privileges Required	Low	Integrity Impact	None
User Interaction	None	Availability Impact	High

CVSS 3.1

Product Status

Vendor	Mattermost
Product	Mattermost
Versions	Default: unaffected affected from 11.9.0 to 11.9.0 (incl.) affected from 11.8.0 to 11.8.4 (incl.) affected from 11.7.0 to 11.7.7 (incl.) affected from 10.11.0 to 10.11.22 (incl.) Version 11.10.0 is unaffected Version 11.9.1 is unaffected Version 11.8.5 is unaffected Version 11.7.8 is unaffected Version 10.11.23 is unaffected

Solutions

Update Mattermost to versions 11.10.0, 11.9.1, 11.8.5, 11.7.8, 10.11.23 or higher.

Credits

alimursaliyev finder

References

MMSA-2026-00719

Problem Types

CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) CWE