CVE-2026-95666 — Unbounded post ID array in the bulk reactions endpoint allows denial of service

CVE-2026-95666

Unbounded post ID array in the bulk reactions endpoint allows denial of service PUBLISHED

Description (CNA)

Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to limit the length of the post ID array accepted by the bulk reactions endpoint which allows an authenticated user to cause excessive database load via a crafted request to {{POST /api/v4/posts/ids/reactions}}.. Mattermost Advisory ID: MMSA-2026-00771

Affected (CNA)

Vendor / product	Versions
Mattermost / Mattermost	affected 11.9.0 through 11.9.1; affected 11.8.0 through 11.8.5; affected 11.7.0 through 11.7.10; affected 11.10.0 through 11.10.1; unaffected 11.11.0; unaffected 11.9.2; unaffected 11.8.6; unaffected 11.7.11; unaffected 11.10.2

CWE

CWE-770

References

https://mattermost.com/security-updates

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.