CVE-2026-11993: Fix authenticated members disabling file content indexing server-wide via extraction pool exhaustion
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 properly enforce the limit of concurrent files being processed and handled failed files, which allows a user with permission to upload files to spawn more goroutines than intended and block the indexing of other files via uploading heavy files constantly to the server.. Mattermost Advisory ID: MMSA-2026-00696
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
Mattermostto a version that resolves this vulnerability.Fixed in 11.10.0 - Upgrade
Upgrade
Mattermostto a version that resolves this vulnerability.Fixed in 11.9.1 - Upgrade
Upgrade
Mattermostto a version that resolves this vulnerability.Fixed in 11.8.5 - Upgrade
Upgrade
Mattermostto a version that resolves this vulnerability.Fixed in 11.7.8 - Upgrade
Upgrade
Mattermostto a version that resolves this vulnerability.Fixed in 10.11.23
Event History
Frequently Asked Questions
Who can exploit this issue?
Any authenticated user who has permission to upload files can exploit it. The attack does not require user interaction or elevated administrative privileges.
What is the practical impact of exploitation?
An attacker can repeatedly upload heavy files to create more extraction-processing goroutines than intended. This can exhaust the extraction pool and block indexing of other users' files across the server.
Which deployments are affected?
Affected versions are Mattermost 11.9.x through 11.9.0, 11.8.x through 11.8.4, 11.7.x through 11.7.7, and 10.11.x through 10.11.22. Exposure depends on users having permission to upload files.
What can be done if updating is not immediately possible?
Restrict file-upload permission for untrusted or unnecessary accounts to reduce who can trigger the condition. Monitor for repeated uploads of heavy files and for file indexing becoming blocked or delayed.