ByteOS Network

NVD Vulnerability Details :

CVE-2026-6339

Analyzed

Source-responsibledisclosure@mattermost.com

Published At-18 May, 2026 | 09:16

Updated At-18 May, 2026 | 19:11

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

Date Added	Due Date	Vulnerability Name	Required Action
	N/A

Metrics

Type	Version	Base score	Base severity	Vector
Secondary	3.1	4.3	MEDIUM	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Primary	3.1	4.3	MEDIUM	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Type: Secondary

Version: 3.1

Base score: 4.3

Base severity: MEDIUM

Vector:

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

Type: Primary

Version: 3.1

Base score: 4.3

Base severity: MEDIUM

Vector:

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

CPE Matches

Mattermost, Inc.

>>mattermost_server>>Versions from 11.4.0(inclusive) to 11.4.4(exclusive)

cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*

Mattermost, Inc.

>>mattermost_server>>Versions from 11.5.0(inclusive) to 11.5.2(exclusive)

cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*

Weaknesses

CWE ID	Type	Source
CWE-346	Secondary	responsibledisclosure@mattermost.com

CWE ID: CWE-346

Type: Secondary

Source: responsibledisclosure@mattermost.com

References

Hyperlink	Source	Resource
https://mattermost.com/security-updates	responsibledisclosure@mattermost.com	Vendor Advisory

Hyperlink: https://mattermost.com/security-updates

Source: responsibledisclosure@mattermost.com

Resource:

Vendor Advisory

CISA Catalog

Metrics

CPE Matches

Weaknesses

Evaluator Description

Evaluator Impact

Evaluator Solution

Vendor Statements

References

Change History