Mattermost up to 10.11.10/11.2.2/11.3.1/11.4.0 Membership authorization

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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5.7$0-$5k0.00

Summaryinfo

A vulnerability labeled as critical has been found in Mattermost up to 10.11.10/11.2.2/11.3.1/11.4.0. The impacted element is an unknown function of the component Membership Handler. The manipulation results in authorization. This vulnerability is known as CVE-2026-4274. It is possible to launch the attack remotely. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in Mattermost up to 10.11.10/11.2.2/11.3.1/11.4.0. It has been classified as critical. Affected is an unknown part of the component Membership Handler. The manipulation with an unknown input leads to a authorization vulnerability. CWE is classifying the issue as CWE-863. The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to restrict team-level access when processing membership sync from a remote cluster, which allows a malicious remote cluster to grant a user access to an entire private team instead of only the shared channel via sending crafted membership sync messages that trigger team membership assignment. Mattermost Advisory ID: MMSA-2026-00574

The weakness was published by daw10. The advisory is shared for download at mattermost.com. This vulnerability is traded as CVE-2026-4274 since 03/16/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. There are neither technical details nor an exploit publicly available.

Upgrading to version 10.11.11, 11.2.3, 11.3.2, 11.4.1 or 11.5.0 eliminates this vulnerability.

Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.9
VulDB Meta Temp Score: 5.7

VulDB Base Score: 6.3
VulDB Temp Score: 6.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 5.4
CNA Vector (Mattermost): 🔒

CVSSv2info

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

Exploitinginfo

Class: Authorization
CWE: CWE-863 / CWE-285 / CWE-266
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 10.11.11/11.2.3/11.3.2/11.4.1/11.5.0

Timelineinfo

03/16/2026 CVE reserved
03/26/2026 +10 days Advisory disclosed
03/26/2026 +0 days VulDB entry created
03/26/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: mattermost.com
Researcher: daw10
Status: Confirmed

CVE: CVE-2026-4274 (🔒)
GCVE (CVE): GCVE-0-2026-4274
GCVE (VulDB): GCVE-100-353580

Entryinfo

Created: 03/26/2026 13:22
Changes: 03/26/2026 13:22 (64)
Complete: 🔍
Cache ID: 216::103

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