{"id":"EUVD-2026-30749","enisaUuid":"4be14734-cac3-3c31-8375-a26f89471364","description":"Mattermost versions 11.5.x \u003c\u003d 11.5.1, 11.4.x \u003c\u003d 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","datePublished":"May 18, 2026, 8:05:30 AM","dateUpdated":"May 18, 2026, 12:42:01 PM","baseScore":4.3,"baseScoreVersion":"3.1","baseScoreVector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L","references":"https://mattermost.com/security-updates\n","aliases":"CVE-2026-6339\nGHSA-xvcx-mgpc-5xh3\n","assigner":"Mattermost","epss":0.11,"enisaIdProduct":[{"id":"b8fcd11e-644d-3d52-aa0b-0c45788292cb","product":{"name":"Mattermost","vendor":{"name":"Mattermost"}},"product_version":"11.5.0 ≤11.5.1"},{"id":"f16d6484-3da8-31dd-9538-c4d18dfcd5c9","product":{"name":"Mattermost","vendor":{"name":"Mattermost"}},"product_version":"11.4.0 ≤11.4.3"}],"enisaIdVendor":[{"id":"a5470120-8a3d-3968-9526-7507634d21ed","vendor":{"name":"Mattermost"}}],"enisaIdVulnerability":[{"id":"1a9e5ba1-5616-3785-94e4-aee53b3aa51e","vulnerability":{"id":"GHSA-xvcx-mgpc-5xh3","description":"Mattermost doesn\u0027t validate the X-Requested-With header on the burn-on-read reveal endpoint","datePublished":"May 18, 2026, 9:31:48 AM","dateUpdated":"Jun 1, 2026, 3:22:30 PM","baseScore":0.0,"references":"https://nvd.nist.gov/vuln/detail/CVE-2026-6339\nhttps://github.com/mattermost/mattermost/commit/7a339a6438f5a4a5feba6b8de887f17a1378b207\nhttps://github.com/mattermost/mattermost\nhttps://mattermost.com/security-updates\n","enisa_id":"EUVD-2026-30749\n","aliases":"GHSA-xvcx-mgpc-5xh3\nCVE-2026-6339\n","epss":0.0,"dataProcessed":"Nov 1, 2026, 2:00:21 AM","vulnerabilityProduct":[],"vulnerabilityVendor":[]}},{"id":"363da5b2-26d1-3407-a213-717ee1e8192d","vulnerability":{"id":"CVE-2026-6339","description":"Mattermost versions 11.5.x \u003c\u003d 11.5.1, 11.4.x \u003c\u003d 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","datePublished":"May 18, 2026, 8:05:30 AM","dateUpdated":"May 18, 2026, 12:42:01 PM","status":"PUBLISHED","baseScore":4.3,"baseScoreVersion":"3.1","baseScoreVector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L","references":"https://mattermost.com/security-updates\n","enisa_id":"EUVD-2026-30749\n","assigner":"Mattermost","epss":0.11,"dataProcessed":"Nov 1, 2026, 7:18:17 AM","vulnerabilityProduct":[{"id":"7b77f7dc-3758-3ded-a123-413607273b10","product":{"name":"Mattermost","vendor":{"name":"Mattermost"}},"product_version":"11.4.0 ≤11.4.3"},{"id":"8a9069b0-f2ab-31d5-b0b3-cc19ae1684a9","product":{"name":"Mattermost","vendor":{"name":"Mattermost"}},"product_version":"11.5.0 ≤11.5.1"}],"vulnerabilityVendor":[{"id":"43dda296-4ebd-3546-ad3d-d75371d639fb","vendor":{"name":"Mattermost"}}]}}],"enisaIdAdvisory":[]}