CVE-2026-57178
social-auth-core: VK App backend accepts unsigned callback data when auth_key is missing
Impact
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 packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| pip | social-auth-core | < 5.0.0 | 5.0.0 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-3c93-f73f-qc9h
- https://github.com/python-social-auth/social-core/security/advisories/GHSA-3c93-f73f-qc9h
- https://nvd.nist.gov/vuln/detail/CVE-2026-57178
- https://github.com/python-social-auth/social-core/pull/1811
- https://github.com/python-social-auth/social-core/commit/1bfacdd0379e5eb46e169a99ab648b835e9bb6a2
- https://github.com/python-social-auth/social-core/releases/tag/5.0.0