CVE-2026-6339GHSA-XVCX-MGPC-5XH3GO-2026-5769
Missing request origin validation on burn-on-read reveal endpoint
- Published
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- Fix
- Fixed in 11.5.2, 11.4.4, 8.0.0-20260327001745-7a339a6438f5, 5.3.2-0.20260327001745-7a339a6438f5, 11.4.4+incompatible, and 1 more
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
CISA's decision points: whether it is exploited, whether attacks can be automated, and how much control an attacker gets. Assessed (SSVC 2.0.3).What do these mean? →
- Exploitation: none
- Automatable: no
- Technical impact: partial
Summary
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
Timeline
- CVE published
- CISA SSVC assessment
Exploitation: none · Automatable: no · Technical impact: partial
- Record last updated
Affected versions
- Mattermost Mattermost
From 11.5.0 · through 11.5.1; From 11.4.0 · through 11.4.3
- github.com/mattermost/mattermost/server/v8Go
From 11.5.0 · fixed in 11.5.2
- github.com/mattermost/mattermost/server/v8Go
From 11.4.0 · fixed in 11.4.4
- github.com/mattermost/mattermost/server/v8Go
fixed in 8.0.0-20260327001745-7a339a6438f5
- github.com/mattermost/mattermost-serverGo
fixed in 5.3.2-0.20260327001745-7a339a6438f5
- github.com/mattermost/mattermost-serverGo
From 11.4.0+incompatible · fixed in 11.4.4+incompatible; From 11.5.0+incompatible · fixed in 11.5.2+incompatible
- github.com/mattermost/mattermost-server/v5Go
All versions
- github.com/mattermost/mattermost-server/v6Go
All versions