CVE-2026-2578 PUBLISHED

Information Disclosure via WebSocket Event When Deleting Unrevealed Burn on Read Posts

Assigner: Mattermost
Reserved: 16.02.2026 Published: 16.03.2026 Updated: 16.03.2026

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

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
CVSS Score: 4.3

Attack Vector	Network	Scope	Unchanged
Attack Complexity	Low	Confidentiality Impact	Low
Privileges Required	Low	Integrity Impact	None
User Interaction	None	Availability Impact	None

CVSS 3.1

Product Status

Vendor	Mattermost
Product	Mattermost
Versions	Default: unaffected affected from 11.3.0 to 11.3.0 (incl.) Version 11.4.0 is unaffected Version 11.3.1 is unaffected

Solutions

Update Mattermost to versions 11.4.0, 11.3.1 or higher.

Credits

Joshua Rogers finder

References

MMSA-2026-00579

Problem Types

CWE-201: Insertion of Sensitive Information Into Sent Data CWE