In webpy web.py version 0.76, the Session component's _load() method reads the session_id directly from the request cookie and loads the session from the store. The _save() method writes back using the same session_id without rotating it after authentication. This lack of session ID rotation enables session fixation attacks, where an attacker can set or fix a session ID before authentication and maintain that authenticated session.

An attacker can exploit this vulnerability to hijack authenticated sessions by fixing the session ID prior to user login, potentially gaining unauthorized access to the victim's session and associated privileges.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, consider implementing application-level session ID rotation after authentication as a temporary mitigation.