CVE-2026-41425

Summary

There is no CSRF protection on the cache feature on most integrations clients.

Details

In authlib.integrations.starlette_client.OAuth, no CSRF protection is set up when using the cache parameter. When not using the cache parameter, the use of SessionMiddleware ties the client to the auth state, preventing CSRF attacks. With the cache, there is no such mechanism. Other integratons have the same issue, it's not just starlette.

The state parameter is taken from the callback URL and the state is fetched from the cache without checking that it is the same client calling the redirect endpoint as was the one that initiated the auth flow.

This issue is documented in RFC 6749 section 10.12: https://datatracker.ietf.org/doc/html/rfc6749#section-10.12

PoC

• Set up a Starlette integration with a cache
• The attacker starts the auth flow up until before the callback URL is followed.
• The attacked sends the redirect URL to the victim
• The victim now completes the authorisation

Impact

This impacts all users that use the cache to store auth state.

All users will be vulnerable to CSRF attacks and may have an attacker's account tied to their own.

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to 1.6.11, there is no CSRF protection on the cache feature in authlib.integrations.starlette_client.OAuth. This vulnerability is fixed in 1.6.11.

Root has patched CVE-2026-41425 in the Authlib package for Root:PyPI. Multiple fixed versions available.

Root has patched GHSA-jj8c-mmj3-mmgv in the Authlib package for Root:PyPI. Multiple fixed versions available.

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to 1.6.11, there is no CSRF protection on the cache feature in authlib.integrations.starlette_client.OAuth. This vulnerability is fixed in 1.6.11.

These are all security issues fixed in the python313-Authlib-1.9.1-1.1 package on the GA media of openSUSE Tumbleweed.

This update for python-Authlib fixes the following issues

• CVE-2026-41425: Prior to 1.6.11, there is no CSRF protection on the cache feature in authlib.integrations.starlette_client.OAuth (bsc#1263114).
• CVE-2026-44681: Prior to 1.6.12 and 1.7.1, an unauthenticated open redirect in Authlib's OpenIDImplicitGrant and OpenIDHybridGrant authorization endpoint exists (bsc#1266665).

Jay Neiva and Mauro Carrillo discovered that Authlib did not properly validate cryptographic keys embedded in JWT headers. An attacker could possibly use this issue to forge trusted tokens, resulting in authentication and authorization bypass. (CVE-2026-27962)

Jay Neiva and Mauro Carrillo discovered that Authlib incorrectly handled RSA1_5 encrypted tokens. An attacker could possibly use this issue to recover sensitive encrypted information, resulting in information disclosure. (CVE-2026-28490)

Jay Neiva and Mauro Carrillo discovered that Authlib did not properly reject unsupported cryptographic algorithms when validating OpenID Connect ID tokens. An attacker could possibly use this issue to bypass token integrity checks, resulting in authentication bypass. (CVE-2026-28498)

Johnny Deuss discovered that Authlib did not provide cross-site request forgery protection for the OAuth cache feature in its Starlette integration. An attacker could possibly use this issue to perform unauthorized OAuth actions, resulting in cross-site request forgery. This issue only affected Ubuntu 24.04 LTS and Ubuntu 26.04 LTS. (CVE-2026-41425)