Mattermost up to 10.11.13/11.4.3/11.5.1 Command Update API authorization

CVSS Meta Temp Score
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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 10.11.13/11.4.3/11.5.1. It has been classified as problematic. Affected by this issue is some unknown functionality of the component Command Update API. This manipulation causes authorization. This vulnerability appears as CVE-2026-28732. The attack may be initiated remotely. There is no available exploit. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in Mattermost up to 10.11.13/11.4.3/11.5.1. It has been declared as problematic. Affected by this vulnerability is an unknown code block of the component Command Update API. The manipulation with an unknown input leads to a authorization vulnerability. The CWE definition for the vulnerability is 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. As an impact it is known to affect integrity. The summary by CVE is:

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 Fail to enforce slash command trigger-word uniqueness during command updates which allows an authenticated team member with Manage Own Slash Commands permission to hijack and impersonate existing system or custom slash commands via editing their own slash command trigger to an already-registered trigger through the command update API. Mattermost Advisory ID: MMSA-2026-00597

The weakness was presented by mr_anksec. The advisory is shared at mattermost.com. This vulnerability is known as CVE-2026-28732 since 03/16/2026. The exploitation appears to be easy. The attack can be launched remotely. Neither technical details nor an exploit are publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 321516 (Mattermost Server 10.11.x < 10.11.14 / 11.4.x < 11.4.4 / 11.5.x < 11.5.2 Vulnerability (MMSA-2026-00597)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 10.11.14, 11.4.4, 11.5.2 or 11.6.0 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (321516) and EUVD (EUVD-2026-30760). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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: 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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Nessus ID: 321516
Nessus Name: Mattermost Server 10.11.x < 10.11.14 / 11.4.x < 11.4.4 / 11.5.x < 11.5.2 Vulnerability (MMSA-2026-00597)

Threat Intelligenceinfo

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

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Mattermost 10.11.14/11.4.4/11.5.2/11.6.0

Timelineinfo

03/16/2026 CVE reserved
05/18/2026 +62 days Advisory disclosed
05/18/2026 +0 days VulDB entry created
06/18/2026 +31 days VulDB entry last update

Sourcesinfo

Advisory: mattermost.com
Researcher: mr_anksec
Status: Confirmed

CVE: CVE-2026-28732 (🔒)
GCVE (CVE): GCVE-0-2026-28732
GCVE (VulDB): GCVE-100-364453
EUVD: 🔒

Entryinfo

Created: 05/18/2026 12:22
Updated: 06/18/2026 20:40
Changes: 05/18/2026 12:22 (64), 05/18/2026 15:34 (1), 06/18/2026 20:40 (2)
Complete: 🔍
Cache ID: 216::103

If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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