CVE-2026-6339 (GCVE-0-2026-6339)
Vulnerability from cvelistv5 – Published: 2026-05-18 08:05 – Updated: 2026-05-18 12:42
VLAI
EPSS
VEX
Title
Missing request origin validation on burn-on-read reveal endpoint
Summary
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
Severity
4.3 (Medium)
SSVC
Exploitation: none
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-05-18 12:41 UTC
CWE
- CWE-346 - Origin Validation Error
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://mattermost.com/security-updates | vendor-advisory |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Mattermost | Mattermost |
Affected:
11.5.0 , ≤ 11.5.1
(semver)
Affected: 11.4.0 , ≤ 11.4.3 (semver) Unaffected: 11.6.0 Unaffected: 11.5.2 Unaffected: 11.4.4 |
guessed |
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