GitHub Advisoryadvisory · Go

GHSA-xvcx-mgpc-5xh3 Mattermost doesn't validate the X-Requested-With header on the burn-on-read reveal endpoint

MEDIUM Published 2026-05-18 Modified 2026-06-01 Official page ↗
Aliases
CVE-2026-6339
Ecosystem
Go
Packages
github.com/mattermost/mattermost/server/v8, github.com/mattermost/mattermost-server
Severity
Moderate
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Weaknesses
CWE-346
Reviewed
2026-06-01

Affected packages

• Go github.com/mattermost/mattermost/server/v8: >= 11.5.0, < 11.5.2 → fixed in 11.5.2 • Go github.com/mattermost/mattermost/server/v8: >= 11.4.0, < 11.4.4 → fixed in 11.4.4 • Go github.com/mattermost/mattermost/server/v8: < 8.0.0-20260327001745-7a339a6438f5 → fixed in 8.0.0-20260327001745-7a339a6438f5 • Go github.com/mattermost/mattermost-server: < 5.3.2-0.20260327001745-7a339a6438f5 → fixed in 5.3.2-0.20260327001745-7a339a6438f5

Description

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

Related

Alias · CVE (1)

  • CVE-2026-6339 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… vulnerability

Weakness · CWE (1)

  • CWE-346 Origin Validation Error weakness

References