Summary
social-auth-core: VK App backend accepts unsigned callback data when auth_key is missing
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.
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.
The application does not adequately verify the identity of a user, device, or process before granting access. Typical impact: unauthorized access to functions or data reserved for authenticated parties.
CVE-2026-57178 has a CVSS score of 7.4 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (5.0.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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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:
Frequently Asked Questions
- What is CVE-2026-57178? CVE-2026-57178 is a high-severity improper authentication vulnerability in social-auth-core (pip), affecting versions < 5.0.0. It is fixed in 5.0.0. The application does not adequately verify the identity of a user, device, or process before granting access.
- How severe is CVE-2026-57178? CVE-2026-57178 has a CVSS score of 7.4 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of social-auth-core are affected by CVE-2026-57178? social-auth-core (pip) versions < 5.0.0 is affected.
- Is there a fix for CVE-2026-57178? Yes. CVE-2026-57178 is fixed in 5.0.0. Upgrade to this version or later.
- Is CVE-2026-57178 exploitable, and should I be worried? Whether CVE-2026-57178 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-57178 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-57178? Upgrade
social-auth-coreto 5.0.0 or later.