CVE-2026-6850 — Crafted message attachment causes client-side denial of service via markdown parser regex backtracking in Mattermost
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 authentic…
Published: 2026-07-13 · CVSS: 6.5 · CVSS 3.1
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
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7