# CVE-2026-57178: social-auth-core: VK App backend accepts unsigned callback data when auth_key is missing

> Attackers can bypass authentication in the VK App backend by omitting the auth_key, allowing them to impersonate arbitrary VK users.

- **Severity:** High 7.4 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Sep 2026
- **Updated:** 28 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-57178, GHSA-3c93-f73f-qc9h, PYSEC-2026-4165, UBUNTU-CVE-2026-57178

## What is CVE-2026-57178?

CVE-2026-57178 is a high-severity authentication bypass vulnerability in python-social-auth social-core, published on 24 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-347 (Improper Verification of Cryptographic Signature), CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-57178?

3 open source packages ship an affected version, including social-auth-core.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `social-auth-core` | PyPI | All versions | 5.0.0 |
| `social-auth-core` | PyPI | All versions | 5.0.0 |
| `social-auth-core` | PyPI | All versions | 5.0.0 |

## How do I fix CVE-2026-57178?

Upgrade social-auth-core to 5.0.0 or later.

## Is CVE-2026-57178 being exploited?

There is no known exploitation of CVE-2026-57178 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-57178 and fix it if it is affected.

What it is: CVE-2026-57178 is a high-severity authentication bypass vulnerability in python-social-auth social-core, published on 24 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-57178 in the wild and no public exploit code.

Affected packages and fixed versions:
- social-auth-core (PyPI): affected all versions; fixed in 5.0.0
- social-auth-core (PyPI): affected all versions; fixed in 5.0.0
- social-auth-core (PyPI): affected all versions; fixed in 5.0.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-57178/ (Markdown: https://insights.sbomify.com/CVE-2026-57178/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-57178
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-57178
- OSV: https://osv.dev/vulnerability/CVE-2026-57178

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-57178/
Summaries are generated and may contain mistakes; the official description above is the record.