{"id":"CVE-2026-57178","aliases":["GHSA-3c93-f73f-qc9h","PYSEC-2026-4165"],"url":"https://o3.security/vulnerability/CVE-2026-57178","summary":"social-auth-core: VK App backend accepts unsigned callback data when auth_key is missing","details":"### Impact\n\nThe `vk-app` backend accepted VK application callback data without verifying the callback signature when the `auth_key` parameter was omitted.\n\nApplications 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.\n\nThe issue affects only applications using the `vk-app` backend.\n\n### Patches\n\nThe issue has been fixed by requiring `auth_key` to be present and valid before callback data is trusted.\n\nUsers should upgrade to a patched version.\n\nFix:\n\n* https://github.com/python-social-auth/social-core/pull/1811\n\n### Workarounds\n\nApplications that cannot upgrade immediately should disable the `vk-app` backend by removing `social_core.backends.vk.VKAppOAuth2` from `SOCIAL_AUTH_AUTHENTICATION_BACKENDS`.\n\nThere is no complete workaround while continuing to use the vulnerable backend.\n\n### Credits\n\nReported by @lalalala5678 through GitHub private vulnerability reporting.","published":"2026-09-24T17:25:47.225Z","modified":"2026-10-21T02:58:44.720566355Z","cvss":{"score":7.4,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"PyPI","name":"social-auth-core","fixedVersion":"5.0.0"}],"fix":{"url":"https://github.com/python-social-auth/social-core/pull/1811","label":"python-social-auth/social-core#1811"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/57xxx/CVE-2026-57178.json"},{"type":"ADVISORY","url":"https://github.com/python-social-auth/social-core/security/advisories/GHSA-3c93-f73f-qc9h"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-57178"},{"type":"WEB","url":"https://github.com/python-social-auth/social-core/pull/1811"},{"type":"WEB","url":"https://github.com/python-social-auth/social-core/commit/1bfacdd0379e5eb46e169a99ab648b835e9bb6a2"},{"type":"PACKAGE","url":"https://github.com/python-social-auth/social-core"},{"type":"WEB","url":"https://github.com/python-social-auth/social-core/releases/tag/5.0.0"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-21T02:58:44.720566355Z"}}