CVE-2026-3115 - Guest users can view group member IDs without respecting view restrictions

Back Back to CVE browser

MEDIUM

Guest users can view group member IDs without respecting view restrictions

Published Mar 26, 2026

4.3

MEDIUM

CVSS 3.1

EPSS 0.27%

Description

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 apply view restrictions when retrieving group member IDs, which allows authenticated guest users to enumerate user IDs outside their allowed visibility scope via the group retrieval endpoint.. Mattermost Advisory ID: MMSA-2026-00594

Affected products

Vendor Mattermost Product Mattermost Default
unaffected
- Version
  10.11.0
  Status
  affected
  Constraints
  <=10.11.10
- Version
  11.2.0
  Status
  affected
  Constraints
  <=11.2.2
- Version
  11.3.0
  Status
  affected
  Constraints
  <=11.3.1
- Version
  11.4.0
  Status
  affected
  Constraints
  <=11.4.0
- Version
  10.11.11
  Status
  unaffected
  Constraints
  -
- Version
  11.2.3
  Status
  unaffected
  Constraints
  -
- Version
  11.3.2
  Status
  unaffected
  Constraints
  -
- Version
  11.4.1
  Status
  unaffected
  Constraints
  -
- Version
  11.5.0
  Status
  unaffected
  Constraints
  -

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor

Product

Default status

Versions

Mattermost

unaffected

Version	Status	Constraints
10.11.0	affected	<=10.11.10
11.2.0	affected	<=11.2.2
11.3.0	affected	<=11.3.1
11.4.0	affected	<=11.4.0
10.11.11	unaffected	-
11.2.3	unaffected	-
11.3.2	unaffected	-
11.4.1	unaffected	-
11.5.0	unaffected	-

github.com/mattermost/mattermost/server/v8

Go

Introduced 8.0.0-20260105080200-d27a2195068d Fixed 8.0.0-20260217110922-b7d4a1f1f59b
github.com/mattermost/mattermost-server

Go

Introduced 10.11.0-rc1+incompatible Fixed 10.11.11+incompatible
github.com/mattermost/mattermost-server

Go

Introduced 11.2.0-rc1+incompatible Fixed 11.2.3+incompatible
github.com/mattermost/mattermost-server

Go

Introduced 11.3.0-rc1+incompatible Fixed 11.3.2+incompatible
github.com/mattermost/mattermost-server

Go

Introduced 11.4.0+incompatible Fixed 11.4.1+incompatible
github.com/mattermost/mattermost-server/v5

Go

Introduced 0 Fixed not fixed
github.com/mattermost/mattermost-server/v6

Go

Introduced 0 Fixed not fixed

Ecosystem	Package	Introduced	Fixed
Go	github.com/mattermost/mattermost/server/v8	8.0.0-20260105080200-d27a2195068d	8.0.0-20260217110922-b7d4a1f1f59b
Go	github.com/mattermost/mattermost-server	10.11.0-rc1+incompatible	10.11.11+incompatible
Go	github.com/mattermost/mattermost-server	11.2.0-rc1+incompatible	11.2.3+incompatible
Go	github.com/mattermost/mattermost-server	11.3.0-rc1+incompatible	11.3.2+incompatible
Go	github.com/mattermost/mattermost-server	11.4.0+incompatible	11.4.1+incompatible
Go	github.com/mattermost/mattermost-server/v5	0	not fixed
Go	github.com/mattermost/mattermost-server/v6	0	not fixed

Remediation

Vendor solution

Update Mattermost to versions 11.5.0, 11.2.3, 10.11.11, 11.4.1, 11.3.2 or higher.

Weaknesses (1)

CWE-863

Incorrect Authorization

References (3)

https://github.com/advisories/GHSA-mpc7-mm28-f6wq
Advisory
https://mattermost.com/security-updates
vendor-advisoryVendor Advisory
https://nvd.nist.gov/vuln/detail/CVE-2026-3115

Link	Providers	Tags
https://github.com/advisories/GHSA-mpc7-mm28-f6wq		Advisory
https://mattermost.com/security-updates		vendor-advisoryVendor Advisory
https://nvd.nist.gov/vuln/detail/CVE-2026-3115