The current design of the change email address procedure allow to obtain the confirmation code without needing to access the current email address.
Impact
An attacker that can access another user account can use that to achieve a complete take over of the account and lock out the legitimate user.
CVSSv3 score: 4.9 (CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:L/A:N)
References
CWE 330