CVE-2026-57179: social-auth-core has a Session Fixation issue

The partial-pipeline resume mechanism accepted partial_token as a bearer credential without binding it to the browser session that created it.

Applications using resumable partial pipeline steps could allow an attacker to start an authentication flow, obtain a valid partial token and verification data, and cause a victim’s browser to resume that attacker-controlled flow. This could authenticate the victim’s browser as the attacker’s account.

The issue affects applications using partial pipeline steps such as mail_validation or custom steps decorated with @partial.