PYSEC-2026-4165

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Import Source
https://github.com/pypa/advisory-database/blob/main/vulns/social-auth-core/PYSEC-2026-4165.yaml
JSON Data
https://api.osv.dev/v1/vulns/PYSEC-2026-4165
Aliases
Published
2026-10-01T16:38:39Z
Modified
2026-10-01T17:45:17Z
Severity
  • 7.4 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N CVSS Calculator
Summary
social-auth-core: VK App backend accepts unsigned callback data when auth_key is missing
Details

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.

References

Affected packages

PyPI / social-auth-core

Package

Name
social-auth-core
View open source insights on deps.dev
Purl
pkg:pypi/social-auth-core

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected
Fixed
5.0.0

Affected versions

0.*
0.0.1
0.1.0
0.2.0
0.2.1
1.*
1.0.0
1.0.1
1.1.0
1.2.0
1.3.0
1.4.0
1.5.0
1.6.0
1.7.0
2.*
2.0.0
3.*
3.0.0
3.1.0
3.2.0
3.3.0
3.3.1
3.3.2
3.3.3
3.4.0
4.*
4.0.2
4.0.3
4.1.0
4.2.0
4.3.0
4.4.0
4.4.1
4.4.2
4.5.0
4.5.1
4.5.2
4.5.3
4.5.4
4.5.5
4.5.6
4.6.0
4.6.1
4.7.0
4.8.0
4.8.1
4.8.2
4.8.3
4.8.4
4.8.5
4.8.6
4.8.7
4.9.0
4.9.1

Database specific

source 
"https://github.com/pypa/advisory-database/blob/main/vulns/social-auth-core/PYSEC-2026-4165.yaml"