PYSEC-2026-4357
See a problem?- Import Source
- https://github.com/pypa/advisory-database/blob/main/vulns/authlib/PYSEC-2026-4357.yaml
- JSON Data
- https://api.osv.dev/v1/vulns/PYSEC-2026-4357
- Aliases
- Published
- 2026-10-22T22:18:04Z
- Modified
- 2026-10-30T10:00:02Z
- Severity
-
- 4.2 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N CVSS Calculator
- Summary
- [none]
- Details
-
Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to 1.9.0, OpenIDMixin.parse_id_token() reads the nonce_supported decision from the untrusted ID token being validated and sets the expected nonce to null when that claim is the JSON boolean false. In implicit and hybrid relying parties, or applications that directly accept externally supplied ID tokens, an attacker with a captured validly signed token can bypass the nonce-to-session binding and replay the victim's token into an attacker-controlled session. Plain authorization code flow is not affected, and the token must still pass signature, issuer, and audience validation. OpenIDMixin.parse_id_token() trusts nonce_supported in both authlib/integrations/base_client/sync_openid.py and authlib/integrations/base_client/async_openid.py to disable the expected nonce. This issue is fixed in version 1.9.0.
- References
Affected packages
PyPI / authlib
Package
- Name
- authlib
- View open source insights on deps.dev
- Purl
- pkg:pypi/authlib
Affected ranges
- Type
- ECOSYSTEM
- Events
-
Introduced0 Unknown introduced version / All previous versions are affectedFixed1.9.0