4.3

CVE-2026-2578: Information Disclosure via WebSocket Event When Deleting Unrevealed Burn on Read Posts

Analyzed
AliasesGHSA-3rhr-jr63-hwq5GO-2026-4734
Published 16-03-2026Last modified 16-03-2026

Vulnerability summary

CVE-2026-2578 is a medium (CVSS 4.3) vulnerability in mattermost. EPSS estimates a 0.23% chance of exploitation in the next 30 days, higher than 14.2% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 4.3, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
4.3/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.23%
0%100%
Low · -0.07 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 2 · Related 2
OPENSUSE-SU-2026:21483-1SUSE-SU-2026:1135-1

Timeline

  1. 16-03-2026
    PublishedVulnerability first disclosed.
  2. 16-03-2026
    Last modifiedVulnerability information updated.

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 metrics

3 scores · 3 sources · 1 version

EPSS trend

Probability

0.23%

Chance of exploitation in the next 30 days

Percentile

14%

Versus all other CVEs

30-day change

Decrease -0.07 pp

From 0.30% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Github.com/mattermost/mattermost-server2 products
  • v5All versions (No fix recorded)
  • v6All versions (No fix recorded)
Mattermost2 products
Github.com/mattermost1 product
  • mattermost-server< 5.3.2-0.20260127062706-c6b205f0d770 | ≥ 10.11.0-rc1, < 10.11.11 | ≥ 11.2.0-rc1, < 11.2.3 | ≥ 11.3.0-rc1, < 11.3.1 | ≥ 11.3.0-rc1+incompatible, < 11.3.1+incompatible
Github.com/mattermost/mattermost/server1 product
  • v8< 8.0.0-20260127062706-c6b205f0d770

4 vendors · 6 products

References

5 links