CVE-2026-4273 PUBLISHED

Insufficient token rotation validation in remote cluster invite confirmation

Assigner: Mattermost
Reserved: 16.03.2026 Published: 18.05.2026 Updated: 18.05.2026

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to validate that the RefreshedToken differs from the original invite token during remote cluster invite confirmation which allows an authenticated attacker to bypass token rotation and reuse the original invite token via sending a crafted invite confirmation with a RefreshedToken matching the original token. Mattermost Advisory ID: MMSA-2026-00575

Metrics

CVSS 3.1

CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
CVSS Score: 3.7

Attack Vector	Network	Scope	Unchanged
Attack Complexity	High	Confidentiality Impact	None
Privileges Required	None	Integrity Impact	Low
User Interaction	None	Availability Impact	None

CVSS 3.1

Product Status

Vendor	Mattermost
Product	Mattermost
Versions	Default: unaffected affected from 11.5.0 to 11.5.1 (incl.) affected from 10.11.0 to 10.11.13 (incl.) Version 11.6.0 is unaffected Version 11.5.2 is unaffected Version 10.11.14 is unaffected

Solutions

Update Mattermost to versions 11.6.0, 11.5.2, 10.11.14 or higher.

Credits

daw10 finder

References

MMSA-2026-00575

Problem Types

CWE-863: Incorrect Authorization CWE