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
Metrics
Affected Vendors & Products
References
| Link | Providers |
|---|---|
| https://mattermost.com/security-updates |
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History
Mon, 18 May 2026 19:15:00 +0000
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Mattermost mattermost Server
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| CPEs | cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Mattermost mattermost Server
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Mon, 18 May 2026 13:30:00 +0000
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| Metrics |
ssvc
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Mon, 18 May 2026 10:45:00 +0000
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Mattermost
Mattermost mattermost |
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| Vendors & Products |
Mattermost
Mattermost mattermost |
Mon, 18 May 2026 09:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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 | |
| Title | Missing request origin validation on burn-on-read reveal endpoint | |
| Weaknesses | CWE-346 | |
| References |
| |
| Metrics |
cvssV3_1
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Status: PUBLISHED
Assigner: Mattermost
Published:
Updated: 2026-05-18T12:42:01.321Z
Reserved: 2026-04-15T10:27:52.835Z
Link: CVE-2026-6339
Updated: 2026-05-18T12:41:57.464Z
Status : Analyzed
Published: 2026-05-18T09:16:23.573
Modified: 2026-05-18T19:11:13.940
Link: CVE-2026-6339
No data.
OpenCVE Enrichment
Updated: 2026-05-18T10:30:23Z