CVEDB API

Vulnerabilities

Vulnerable Software

Vulnerability Details 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 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

Exploit prediction scoring system (EPSS) score

EPSS Score 0.0

EPSS Ranking 3.9%

CVSS Severity

CVSS v3 Score 4.3

References

https://mattermost.com/security-updates

Products affected by CVE-2026-6339

Mattermost » Mattermost Server » Version: 11.4.0

cpe:2.3:a:mattermost:mattermost_server:11.4.0
Mattermost » Mattermost Server » Version: 11.4.1

cpe:2.3:a:mattermost:mattermost_server:11.4.1
Mattermost » Mattermost Server » Version: 11.4.2

cpe:2.3:a:mattermost:mattermost_server:11.4.2
Mattermost » Mattermost Server » Version: 11.4.3

cpe:2.3:a:mattermost:mattermost_server:11.4.3
Mattermost » Mattermost Server » Version: 11.5.0

cpe:2.3:a:mattermost:mattermost_server:11.5.0
Mattermost » Mattermost Server » Version: 11.5.1

cpe:2.3:a:mattermost:mattermost_server:11.5.1

Vulnerabilities

Vulnerable Software

Vulnerability Details CVE-2026-6339

Products

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