Trendnet AC2600 TEW-827DRU version 2.08B01 contains a flaw in the session management for the device. The router's management software manages web sessions based on IP address rather than verifying client cookies/session tokens/etc. This allows an attacker (whether from a different computer, different web browser on the same machine, etc.) to take over an existing session. This does require the attacker to be able to spoof or take over original IP address of the original user's session.

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-20151
• https://www.tenable.com/security/research/tra-2021-54