CVE-2026-2578

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

Affected packages (6)

• Go/github.com/mattermost/mattermost-serverfrom 0, < 5.3.2-0.20260127062706-c6b205f0d770
• Go/github.com/mattermost/mattermost-server>= 10.11.0-rc1+incompatible, < 10.11.11+incompatible, >= 11.2.0-rc1+incompatible, < 11.2.3+incompatible, >= 11.3.0-rc1+incompatible, < 11.3.1+incompatible
• Go/github.com/mattermost/mattermost-server/v5from 0
• Go/github.com/mattermost/mattermost-server/v6from 0
• Go/github.com/mattermost/mattermost/server/v8from 0, < 8.0.0-20260127062706-c6b205f0d770
• Go/github.com/mattermost/mattermost/server/v8from 0, < 8.0.0-20260127062706-c6b205f0d770

CVSS scores

References (5)

• ADVISORYhttps://github.com/advisories/GHSA-3rhr-jr63-hwq5
• ADVISORYhttps://nvd.nist.gov/vuln/detail/CVE-2026-2578
• PATCHhttps://github.com/mattermost/mattermost
• WEBhttps://github.com/mattermost/mattermost/commit/c6b205f0d77080ef805783de0628b9526af7faec
• WEBhttps://mattermost.com/security-updates