CVE-2026-6339 — Missing request origin validation on burn-on-read reveal endpoint
Mattermost versions 11.5.x <= 11.5.1, 11.4.x <= 11.4.3 fail to validate the X-Requested-With header on the burn-on-read reveal endpoint which allows an authenticated channel mem…
Published: 2026-05-18 · CVSS: 4.3 · CVSS 3.1
Mattermost versions 11.5.x <= 11.5.1, 11.4.x <= 11.4.3 fail to validate the X-Requested-With header on the burn-on-read reveal endpoint which allows an authenticated channel member to force the reveal of a burn-on-read message without recipient consent via a crafted Markdown image tag.. Mattermost Advisory ID: MMSA-2026-00636
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7