# CVE-2026-104056: Authlib OAuth/OIDC discovery metadata cache trust boundary bypass

Source: https://junglewise.ai/threats/cve-2026-104056-authlib-version-1-7-2-and-below-contains-a-vulnerability-where  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-01. Updated: 2026-10-05  
License: CC BY 4.0 with a link back

CVE-2026-104056 · Severity: info · Published 2026-10-01

Authlib is a Python library that handles OAuth and OpenID Connect authentication. Versions 1.7.2 and below accept OpenID discovery documents without verifying that returned endpoint URLs belong to the legitimate identity provider, allowing attackers to redirect authentication flows to malicious servers. An attacker positioned to tamper with discovery responses could intercept credentials including authorization codes, access tokens, and client secrets.

Technologies: [Authlib](https://junglewise.ai/threats/technologies/authlib-authlib). Vendors: [Authlib](https://junglewise.ai/threats/vendors/authlib).

## Quick answers

**Is CVE-2026-104056 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-104056 being exploited in the wild.

**How severe is CVE-2026-104056?** Informational severity, published 1 October 2026.

**Which products and versions are affected?** Authlib 1.7.2 and below.

**Is there a fix for CVE-2026-104056?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-104056 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-104056?** Check whether you run Authlib at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability exists in load_server_metadata(), which caches OpenID Connect discovery JSON without binding endpoint URLs to the issuer origin. AuthorizationServerMetadata.validate() performs only format checks (HTTPS, well-formed URL) and lacks origin validation. Downstream consumers—fetch_access_token(), fetch_jwk_set(), userinfo(), authorize_redirect()—blindly trust the cached metadata and send HTTP requests or browser redirects to attacker-controlled endpoints. Attack requires a network position to poison discovery responses (compromised CDN, network interception, or misconfigured TLS termination).

## Affected products

- Authlib Authlib 1.7.2 and below

## Timeline

- 2026-10-01: disclosed

## References

- [https://uziii2208.github.io/post/cve-2026-104056/](https://uziii2208.github.io/post/cve-2026-104056/)

## Related threats

- [Authlib client configuration endpoint authorization bypass](https://junglewise.ai/threats/cve-2026-116672-authlib-is-a-python-library-which-builds-oauth-and-openid)
- [Authlib RFC 9101 server-side request forgery in request_uri parameter](https://junglewise.ai/threats/cve-2026-114620-authlib-is-a-python-library-which-builds-oauth-and-openid)
- [Authlib OpenID Connect scope validation bypass](https://junglewise.ai/threats/cve-2026-114619-authlib-is-a-python-library-which-builds-oauth-and-openid)
- [Authlib JWT Bearer Grant audience validation bypass](https://junglewise.ai/threats/cve-2026-114618-authlib-is-a-python-library-which-builds-oauth-and-openid)
- [Authlib nonce validation bypass in OpenID token parsing](https://junglewise.ai/threats/cve-2026-114617-authlib-is-a-python-library-which-builds-oauth-and-openid)