{"id":"CVE-2026-6339","revision":"637e22ec636d463fb3a5ba31a2f4e675","records":[{"revision":"637e22ec636d463fb3a5ba31a2f4e675","observedAt":"2026-10-25T14:19:28.838+00:00","statement":{"source":"nvd","id":"CVE-2026-6339","aliases":[],"title":"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 recip…","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","state":0,"publishedAt":"2026-05-18T09:16:23.573+00:00","modifiedAt":"2026-10-14T20:10:00.19+00:00","affected":[],"metrics":[{"system":"CVSS 3.1 · responsibledisclosure@mattermost.com · Secondary","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L","score":4.3,"severity":"MEDIUM"},{"system":"CVSS 3.1 · nvd@nist.gov · Primary","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N","score":4.3,"severity":"MEDIUM"}],"references":["https://mattermost.com/security-updates"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-6339","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Analyzed","weaknesses":["CWE-346"],"productCriteria":["cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*"],"sourceDates":{"published":"2026-05-18T09:16:23.573","lastModified":"2026-10-14T20:10:00.190"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-6339","identifiers":["CVE-2026-6339"]},"retained":false,"historicalAffected":[]}],"coverage":[]}