CVE-2026-9162 - Global session revocation does not invalidate active WebSocket connections

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MEDIUM

Global session revocation does not invalidate active WebSocket connections

Published Jun 22, 2026

4.3

MEDIUM

CVSS 3.1

EPSS 0.33%

Description

Mattermost versions 11.7.x <= 11.7.0, 11.6.x <= 11.6.2, 11.5.x <= 11.5.5, 10.11.x <= 10.11.17 fail to invalidate cached authentication state for active WebSocket connections during global session revocation, which allows a user with an existing WebSocket connection to remain authenticated and continue receiving real-time events until the cached session expires or the client reconnects.. Mattermost Advisory ID: MMSA-2026-00664

Affected products

Vendor Mattermost Product Mattermost Default
unaffected
- Version
  10.11.0
  Status
  affected
  Constraints
  <=10.11.17
- Version
  11.5.0
  Status
  affected
  Constraints
  <=11.5.5
- Version
  11.6.0
  Status
  affected
  Constraints
  <=11.6.2
- Version
  11.7.0
  Status
  affected
  Constraints
  <=11.7.0
- Version
  10.11.18
  Status
  unaffected
  Constraints
  -
- Version
  11.5.6
  Status
  unaffected
  Constraints
  -
- Version
  11.6.3
  Status
  unaffected
  Constraints
  -
- Version
  11.7.1
  Status
  unaffected
  Constraints
  -
- Version
  11.8.0
  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	<=10.11.17
11.5.0	affected	<=11.5.5
11.6.0	affected	<=11.6.2
11.7.0	affected	<=11.7.0
10.11.18	unaffected	-
11.5.6	unaffected	-
11.6.3	unaffected	-
11.7.1	unaffected	-
11.8.0	unaffected	-

github.com/mattermost/mattermost-server

Go

Introduced 10.11.0+incompatible Fixed 10.11.18+incompatible
github.com/mattermost/mattermost-server

Go

Introduced 11.5.0+incompatible Fixed 11.5.6+incompatible
github.com/mattermost/mattermost-server

Go

Introduced 11.6.0+incompatible Fixed 11.6.3+incompatible
github.com/mattermost/mattermost-server

Go

Introduced 11.7.0+incompatible Fixed 11.7.1+incompatible

Ecosystem	Package	Introduced	Fixed
Go	github.com/mattermost/mattermost-server	10.11.0+incompatible	10.11.18+incompatible
Go	github.com/mattermost/mattermost-server	11.5.0+incompatible	11.5.6+incompatible
Go	github.com/mattermost/mattermost-server	11.6.0+incompatible	11.6.3+incompatible
Go	github.com/mattermost/mattermost-server	11.7.0+incompatible	11.7.1+incompatible

Remediation

Vendor solution

Update Mattermost to versions 11.8.0, 11.7.1, 11.6.3, 11.5.6, 10.11.18 or higher.

Weaknesses (1)

CWE-613

References (3)

https://github.com/advisories/GHSA-h998-hxxj-8q83
Advisory
https://mattermost.com/security-updates
vendor-advisoryVendor Advisory
https://nvd.nist.gov/vuln/detail/CVE-2026-9162

Link	Providers	Tags
https://github.com/advisories/GHSA-h998-hxxj-8q83		Advisory
https://mattermost.com/security-updates		vendor-advisoryVendor Advisory
https://nvd.nist.gov/vuln/detail/CVE-2026-9162