CVE-2026-6339

MEDIUM EPSS 1.7%
Published May 18, 20261mo ago · Modified Jun 17, 20262w ago
4.3 CVSS 3.1
Medium
Find Similar
Published May 18, 2026 1mo ago
Last Modified Jun 17, 2026 2w ago

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

CVSS Details

Base Score
4.3
Exploitability
2.8
Impact
1.4
Vector string
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Attack Vector Network
Attack Complexity Low
Privileges Required Low
User Interaction None
Scope Unchanged
Confidentiality Low
Integrity None
Availability None

Threat Intelligence

EPSS Exploit Probability
1.7% percentile
Exploit & Patch Status
No Known Exploit
No Patch Available

Weaknesses 1

CWE-346

Affected Products 2

VendorProductVersionRange
mattermostmattermost_server*≥11.4.0  –  <11.4.4
mattermostmattermost_server*≥11.5.0  –  <11.5.2

References 1

  • mattermost.com https://mattermost.com/security-updates
    Vendor Advisory

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.