Mattermost allows a removed team member to enumerate all public channels within a private team

CVE-2026-2458 → View on GitHub ↗ View on CVE.org ↗ View on NVD ↗

Description

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly validate team membership when searching channels which allows a removed team member to enumerate all public channels within a private team via the channel search API endpoint. Mattermost Advisory ID: MMSA-2025-00568

Basic information

Type
reviewed
Severity
medium
Advisory on GitHub
Open advisory ↗
Repository advisory
—
Source code
Browse source ↗
Published (advisory)
2026-03-16 15:30:43 UTC
Updated
2026-03-17 20:01:41 UTC
GitHub reviewed
2026-03-17 20:01:40 UTC
NVD published
2026-03-16

EPSS Score

Score Percentile
0.03% 9.96%

CVSS Scores

Base score Version Severity Vector
4.3 3.1 —
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.

Identifiers

Type Value
GHSA GHSA-679f-wmrg-qf57 ↗
CVE CVE-2026-2458 ↗

CWEs

CWE id Name
CWE-862 Missing Authorization

Affected packages (5)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
go github.com/mattermost/mattermost/server/v8 < 8.0.0-20260113182106-a18b80ba4c32 8.0.0-20260113182106-a18b80ba4c32 —
go github.com/mattermost/mattermost-server < 5.3.2-0.20260113182106-a18b80ba4c32 5.3.2-0.20260113182106-a18b80ba4c32 —
go github.com/mattermost/mattermost-server >= 10.11.0-rc1, < 10.11.11 10.11.11 —
go github.com/mattermost/mattermost-server >= 11.2.0-rc1, < 11.2.3 11.2.3 —
go github.com/mattermost/mattermost-server >= 11.3.0-rc1, < 11.3.1 11.3.1 —

References

cvelogic Threat Intelligence