CVE-2026-57178: Python-Social-Auth Social-Core

High severity, CVSS 7.4. EPSS: 0.2% chance of exploitation in the next 30 days.

Python Social Auth is a social authentication/registration mechanism. Prior to version 5.0.0, the `vk-app` backend accepted VK application callback data without verifying the callback signature when the `auth_key` parameter was omitted. Applications using this backend could treat unsigned attacker-controlled data as a verified VK identity. An attacker could choose callback fields such as `viewer_id`, `access_token`, `api_id`, and `api_result`, potentially allowing authentication as an arbitrary VK user ID. The issue affects only applications using the `vk-app` backend. The issue has been fixed in version 5.0.0 by requiring `auth_key` to be present and valid before callback data is trusted.

Affected products

• Python-Social-Auth Social-Core: before 5.0.0 (fixed in 5.0.0)

Published 2026-09-24. Last modified 2026-09-28.