What is the CVSS score of CVE-2026-21386?

CVE-2026-21386 has a CVSS 3.1 base score of 4.3 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N. EPSS exploitation probability: 0.0%.

Which versions of Mattermost Server are affected by CVE-2026-21386?

CVE-2026-21386 presents moderate security risk rated CVSS 4.3. Exploitation could compromise the security of affected deployments.. A patch is available.

How to fix or mitigate CVE-2026-21386?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Monitor vendor channels for patch availability.

Mattermost Server CVE-2026-21386

EUVD-2026-12437 MEDIUM

Observable Discrepancy (CWE-203)

2026-03-16 responsibledisclosure@mattermost.com

GHSA-5mr9-crcg-8wh2

Information Disclosure Mattermost Server Suse

4.3

CVSS 3.1 · NVD

Severity by source

NVD PRIMARY

4.3 MEDIUM

AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

SUSE

MEDIUM

qualitative

Primary rating from NVD.

CVSS VectorNVD

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

None

Lifecycle Timeline

Patch released

Mar 31, 2026 - 21:13 nvd

Patch available

EUVD ID Assigned

Mar 16, 2026 - 15:30 euvd

EUVD-2026-12437

Analysis Generated

Mar 16, 2026 - 15:30 vuln.today

CVE Published

Mar 16, 2026 - 15:16 nvd

MEDIUM 4.3

DescriptionCVE.org

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to use consistent error responses when handling the /mute command which allows an authenticated team member to enumerate private channels they are not authorized to know about via differing error messages for nonexistent versus private channels. Mattermost Advisory ID: MMSA-2026-00588

AnalysisAI

CVE-2026-21386 is a security vulnerability (CVSS 4.3) that allows an authenticated team member. Remediation should follow standard vulnerability management procedures.

Technical ContextAI

Vulnerability type not specified by vendor.

RemediationAI

Monitor vendor channels for patch availability.

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Vendor StatusVendor

SUSE

Severity: Medium

Product	Status
openSUSE Leap 15.6	Fixed
SUSE Linux Enterprise Module for Package Hub 15 SP5	Fixed
SUSE Linux Enterprise Module for Package Hub 15 SP6	Fixed
openSUSE Leap 15.5	Fixed

CVE-2026-21386 vulnerability details – vuln.today

Back

Mattermost Server CVE-2026-21386

Severity by source

CVSS VectorNVD

Lifecycle Timeline

DescriptionCVE.org

AnalysisAI

Technical ContextAI

RemediationAI

More in Mattermost Server

Same weakness CWE-203 – Observable Discrepancy

Same technique Information Disclosure

Vendor StatusVendor

SUSE

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External POC / Exploit Code