Medium severity · published Mar 16, 2026
CVE-2026-2578
Information Disclosure via WebSocket Event When Deleting Unrevealed Burn on Read Posts
4.3
CVSS
0.2%
EPSS
No
On KEV
Description
Mattermost versions 11.3.x <= 11.3.0 fail to preserve the redacted state of burn-on-read posts during deletion which allows channel members to access unrevealed burn-on-read message contents via the WebSocket post deletion event.. Mattermost Advisory ID: MMSA-2026-00579
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
Low
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 14% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MA
Mattermost · Mattermost
11.3.0 through 11.3.0 · source: vendor
MS
Mattermost Server · Mattermost
11.3.0 before 11.3.1 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-2578
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-2578
Vendor Advisory
https://mattermost.com/security-updates
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