CVE-2026-6339

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Source
https://cve.org/CVERecord?id=CVE-2026-6339
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-6339.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-6339
Aliases
Published
2026-05-18T08:05:30.925Z
Modified
2026-07-08T08:13:48.541563108Z
Severity
  • 4.3 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L CVSS Calculator
Summary
Missing request origin validation on burn-on-read reveal endpoint
Details

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

Database specific 
{
    "unresolved_ranges": [
        {
            "source": "AFFECTED_FIELD",
            "extracted_events": [
                {
                    "introduced": "11.5.0"
                },
                {
                    "last_affected": "11.5.1"
                },
                {
                    "introduced": "11.4.0"
                },
                {
                    "last_affected": "11.4.3"
                }
            ]
        }
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/6xxx/CVE-2026-6339.json",
    "cna_assigner": "Mattermost",
    "cwe_ids": [
        "CWE-346"
    ]
}
References

Affected packages

Git / github.com/mattermost/mattermost

Affected ranges

Type
GIT
Repo
https://github.com/mattermost/mattermost
Events
Introduced
2a1ac98bd3fae587927adf9340ba266c8c02018e
Fixed
37b08cfe7154241c2c6a8af0fd500e0785bbc900
Introduced
9f2616376582893035a7e3cb38b0fab648bba4e8
Fixed
cc4ef6863ee114bc96be4e34478ec2f0db3eac4e
Database specific 
{
    "source": "CPE_RANGE",
    "cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
    "extracted_events": [
        {
            "introduced": "11.4.0"
        },
        {
            "fixed": "11.4.4"
        },
        {
            "introduced": "11.5.0"
        },
        {
            "fixed": "11.5.2"
        }
    ]
}

Affected versions

@mattermost/client@11.*
@mattermost/client@11.4.0
@mattermost/types@11.*
@mattermost/types@11.4.0
mattermost-redux@11.*
mattermost-redux@11.4.0
v11.*
v11.4.0
v11.4.0-rc3
v11.4.1
v11.4.1-rc1
v11.4.1-rc2
v11.4.2
v11.4.3
v11.5.0
v11.5.1
v11.5.2-rc1
v11.5.2-rc2

Database specific

source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-6339.json"