Mattermost up to 10.11.10/11.2.2/11.3.0 /mute information exposure

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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4.2$0-$5k0.00

Summaryinfo

A vulnerability was found in Mattermost up to 10.11.10/11.2.2/11.3.0 and classified as problematic. This issue affects some unknown processing of the file /mute. Such manipulation leads to information exposure. This vulnerability is listed as CVE-2026-21386. The attack may be performed from remote. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Mattermost up to 10.11.10/11.2.2/11.3.0. It has been rated as problematic. Affected by this issue is an unknown code of the file /mute. The manipulation with an unknown input leads to a information exposure vulnerability. Using CWE to declare the problem leads to CWE-203. 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. Impacted is confidentiality. CVE summarizes:

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

The weakness was presented by winfunc. The advisory is available at mattermost.com. This vulnerability is handled as CVE-2026-21386 since 02/13/2026. The exploitation is known to be easy. The attack may be launched remotely. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1592 by the MITRE ATT&CK project.

Upgrading to version 10.11.11, 11.2.3, 11.3.1 or 11.4.0 eliminates this vulnerability.

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Productinfo

Type

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.3
VulDB Meta Temp Score: 4.2

VulDB Base Score: 4.3
VulDB Temp Score: 4.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 4.3
CNA Vector (Mattermost): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Information exposure
CWE: CWE-203 / CWE-200 / CWE-284
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Mattermost 10.11.11/11.2.3/11.3.1/11.4.0

Timelineinfo

02/13/2026 CVE reserved
03/16/2026 +31 days Advisory disclosed
03/16/2026 +0 days VulDB entry created
03/21/2026 +5 days VulDB entry last update

Sourcesinfo

Advisory: mattermost.com
Researcher: winfunc
Status: Confirmed

CVE: CVE-2026-21386 (🔒)
GCVE (CVE): GCVE-0-2026-21386
GCVE (VulDB): GCVE-100-351278

Entryinfo

Created: 03/16/2026 16:16
Updated: 03/21/2026 11:50
Changes: 03/16/2026 16:16 (65), 03/21/2026 11:50 (1)
Complete: 🔍
Cache ID: 216::103

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