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CVE-2026-21386

nvd nist
Published: Mar 16, 2026Modified: Jun 17, 2026

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4.3
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Exploitability: 2.8 / Impact: 1.4
Source: responsibledisclosure@mattermost.com (Secondary)

Description

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

Affected (3)

Mattermost
1 product
Mattermost Server
Configuration A
3 vulnerable
Vulnerable SoftwareAffected Versions
Mattermost
Mattermost Server
From 10.11.0 to 10.11.11
Mattermost Server
From 11.2.0 to 11.2.3
Mattermost Server
From 11.3.0 to 11.3.1

Related CWEs

CWE-203
Observable Discrepancy
The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor, which exposes security-relevant information about the state of the product, such as whether a particular operation was successful or not.

References (1)

Source: responsibledisclosure@mattermost.com
Vendor Advisory

Timeline

No history available yet.