social-auth-core: VK App backend accepts unsigned callback data when auth_key is missing
Impact
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.
Patches
The issue has been fixed by requiring auth_key to be present and valid before callback data is trusted.
Users should upgrade to a patched version.
Fix:
Workarounds
Applications that cannot upgrade immediately should disable the vk-app backend by removing social_core.backends.vk.VKAppOAuth2 from SOCIAL_AUTH_AUTHENTICATION_BACKENDS.
There is no complete workaround while continuing to use the vulnerable backend.
Credits
Reported by @lalalala5678 through GitHub private vulnerability reporting.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | social-auth-core | < 5.0.0 | 5.0.0 |
References
- 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
- https://github.com/python-social-auth/social-core/releases/tag/5.0.0
- https://pypi.org/project/social-auth-core
- https://github.com/advisories/GHSA-3c93-f73f-qc9h
- CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N- Weakness (CWE)
CWE-287, CWE-347- Platform
- Python (PyPI)
- Package
social-auth-core- Disclosed
- 24.09.2026
- Updated
- 11.10.2026 15:18
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-4165 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-3c93-f73f-qc9h - CC BY 4.0
Vulnerability history: social-auth-core
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 5
- First → latest
- 09.2026 09.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 1
- Medium 4
Disclosures per year
- 2026: 5
-
social-auth-core: VK App backend accepts unsigned callback data when auth_key is missing this entry
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