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

Vulnerability summary

CVE-2026-57179 is a medium (CVSS 4.2) Session Fixation vulnerability in python-social-auth social-core. EPSS estimates a 0.16% chance of exploitation in the next 30 days, higher than 4.9% of scored vulnerabilities.

Timeline

1. 24-09-2026
   PublishedVulnerability first disclosed.
2. 24-09-2026
   Last modifiedVulnerability information updated.

Description

Python Social Auth is a social authentication/registration mechanism. Prior to version 5.0.0, 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`. The issue has been fixed in version 5.0.0 by binding partial pipeline resumes to the originating browser session.

• CWE-384Session FixationAuthenticating a user, or otherwise establishing a new user session, without invalidating any existing session identifier gives an attacker the opportunity to steal authenticated sessions.