Vulnerability · Published Mar 16, 2026 · Assigned by Mattermost
CVE-2026-2578Information Disclosure via WebSocket Event When Deleting Unrevealed Burn on Read Posts
Medium 4.3
In plain English
A medium-severity security flaw in Mattermost from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 14% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Severity (CVSS 3.1)4.3Medium
Exploit odds (30 days)0.2%top 85.7% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official 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 & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | 11.2.3 | GHSA-3rhr-jr63-hwq5 |
| Go | github.com/mattermost/mattermost-server | 5.3.2-0.20260127062706-c6b205f0d770 | GHSA-3rhr-jr63-hwq5 |
| Go | github.com/mattermost/mattermost-server | 10.11.11 | GHSA-3rhr-jr63-hwq5 |
| Go | github.com/mattermost/mattermost-server | 11.3.1 | GHSA-3rhr-jr63-hwq5 |
| Go | github.com/mattermost/mattermost-server | 10.11.11+incompatible, 11.2.3+incompatible, 11.3.1+incompatible | GO-2026-4734 |
| Go | github.com/mattermost/mattermost-server/v5 | no fix listed | GO-2026-4734 |
| Go | github.com/mattermost/mattermost-server/v6 | no fix listed | GO-2026-4734 |
| Go | github.com/mattermost/mattermost/server/v8 | 8.0.0-20260127062706-c6b205f0d770 | GO-2026-4734 |
| Go | github.com/mattermost/mattermost/server/v8 | 8.0.0-20260127062706-c6b205f0d770 | GHSA-3rhr-jr63-hwq5 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mattermost | Mattermost | 11.3.0 – through 11.3.0 |
Weakness: CWE-201 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
References
- MMSA-2026-00579 vendor-advisory