CVE-2026-10600: Denial of service via unbounded document content extraction in Mattermost Server

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-27 · updated 2026-08-03
Weakness: CWE-770

Description

Mattermost versions 11.8.x <= 11.8.0, 11.7.x <= 11.7.3, 11.6.x <= 11.6.5, 10.11.x <= 10.11.20 fail to bound the time and resource consumption of server-side document content extraction which allows an authenticated user with file-upload permission to degrade file uploads for all users on the server via repeatedly uploading small documents that are cheap to upload but expensive to extract, saturating the shared extraction worker pool.. Mattermost Advisory ID: MMSA-2026-00694

Affected products

Mattermost: from 10.11.0 before 10.11.21; from 11.6.0 before 11.6.6; from 11.7.0 before 11.7.4; from 11.8.0 before 11.8.1 — fixed in 10.11.21, 11.6.6, 11.7.4, 11.8.1

How to fix

Upgrade to a fixed version: Mattermost 10.11.21, 11.6.6, 11.7.4, 11.8.1. Check the vendor advisory for mitigations.

References

https://mattermost.com/security-updates

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