Description
Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to validate the length and content of message attachment field values, which allows an authenticated attacker to cause a denial of service for all users in a channel via a post containing a specially crafted payload that triggers catastrophic backtracking in the client-side markdown parser.. Mattermost Advisory ID: MMSA-2026-00658
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Mattermost | Mattermost | 11.7.0 – ≤ 11.7.2, 11.6.0 – ≤ 11.6.4, 10.11.0 – ≤ 10.11.19 | 11.8.0 |
Advisories 1
- WID-SEC-2026-1932 Mattermost: Mehrere Schwachstellen ermöglichen nicht spezifizierten Angriff BSI CERT-Bund (WID) · Jul 13, 2026
References
- MMSA-2026-00658 vendor-advisory