# CVE-2026-114618: Authlib JWT Bearer Grant audience validation bypass

Source: https://junglewise.ai/threats/cve-2026-114618-authlib-is-a-python-library-which-builds-oauth-and-openid  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-22. Updated: 2026-10-22  
License: CC BY 4.0 with a link back

CVE-2026-114618 · Severity: medium · CVSS 6.8 · Published 2026-10-22

Authlib is a Python library that implements OAuth and OpenID Connect servers. Prior to version 1.9.0, the default JWT Bearer Grant implementation fails to validate the audience claim, allowing an attacker with a valid JWT token issued for another service to obtain an access token if the services share the same signing key. This enables unauthorized cross-service access.

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

## Quick answers

**Is CVE-2026-114618 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-114618 being exploited in the wild.

**How severe is CVE-2026-114618?** Medium severity, with a CVSS score of 6.8, published 22 October 2026.

**Which products and versions are affected?** Authlib prior to 1.9.0; authlib (PyPI) < 1.9.0, ECOSYSTEM:introduced=0,fixed=1.9.0.

**Is there a fix for CVE-2026-114618?** Yes. authlib (PyPI): upgrade to 1.9.0 or later. Until then: Implementations can override the get_audiences() method with the server's valid audience identifiers to avoid this vulnerability until upgrading. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-114618 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-114618?** Check whether you run Authlib or authlib (PyPI) 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.

## How to fix

- authlib (PyPI): upgrade to 1.9.0 or later

  ```sh
  pip install "authlib>=1.9.0"
  ```


Implementations can override the get_audiences() method with the server's valid audience identifiers to avoid this vulnerability until upgrading.

## Technical details

The JWTBearerGrant.get_audiences() method returns an empty list by default, causing JWTBearerGrant.verify_claims() to accept any JWT with an aud claim present without matching it against the authorization server's valid audience identifiers. An attacker can exploit this by presenting a legitimate assertion intended for another service to obtain an access token, bypassing the audience validation. The fix in version 1.9.0 enforces that get_audiences() must return a non-empty list of valid audience identifiers.

## Affected products

- Authlib Authlib prior to 1.9.0

## Identifiers

- CVE-2026-114618
- GHSA-fch4-3c6x-j4gc
- PYSEC-2026-4358

## Timeline

- 2026-10-22: disclosed
- 2026-10-08: patched

## References

- [https://github.com/authlib/authlib/commit/e3bd41cb29dcfee434453b135ffb487884baeedf](https://github.com/authlib/authlib/commit/e3bd41cb29dcfee434453b135ffb487884baeedf)
- [https://github.com/authlib/authlib/pull/945](https://github.com/authlib/authlib/pull/945)

## 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 nonce validation bypass in OpenID token parsing](https://junglewise.ai/threats/cve-2026-114617-authlib-is-a-python-library-which-builds-oauth-and-openid)
- [Authlib HMAC signature forgery with zero-length keys](https://junglewise.ai/threats/cve-2026-114616-authlib-is-a-python-library-which-builds-oauth-and-openid)