CVE-2026-2458
Improper Access Control in Mattermost Allows Channel Enumeration
Publication date: 2026-03-16
Last updated on: 2026-03-18
Assigner: Mattermost, Inc.
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| mattermost | mattermost_server | From 10.11.0 (inc) to 10.11.11 (exc) |
| mattermost | mattermost_server | From 11.2.0 (inc) to 11.2.3 (exc) |
| mattermost | mattermost_server | From 11.3.0 (inc) to 11.3.1 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-862 | The product does not perform an authorization check when an actor attempts to access a resource or perform an action. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability exists in certain versions of Mattermost (11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10) where the system fails to properly validate team membership during channel searches.
Because of this improper validation, a user who has been removed from a private team can still enumerate all public channels within that private team by using the channel search API endpoint.
How can this vulnerability impact me? :
The impact of this vulnerability is that a removed team member can gain information about public channels inside a private team that they should no longer have access to.
This could lead to unauthorized disclosure of information about team structure or channel existence, potentially aiding further reconnaissance or social engineering attacks.
The CVSS base score of 4.3 indicates a low to medium severity impact, specifically limited to confidentiality (partial information disclosure) without affecting integrity or availability.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
What immediate steps should I take to mitigate this vulnerability?
I don't know