Read the docs
TI-2026-22761 Aliases CVE-2026-28498GHSA-m344-f55w-2m6j

Authlib: Fail-Open Cryptographic Verification in OIDC Hash Binding

Priority HIGH 69CWE-354Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
High
Attack requirements
Present
Impact type
—
Confidentiality · integrity · availability
None · High · None
Fix status
Partial Red Hat: 5 fixed, 2 without a fix

Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat.

Summary

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a library-level vulnerability was identified in the Authlib Python library concerning the validation of OpenID Connect (OIDC) ID Tokens. Specifically, the internal hash verification logic (_verify_hash) responsible for validating the at_hash (Access Token Hash) and c_hash (Authorization Code Hash) claims exhibits a fail-open behavior when encountering an unsupported or unknown cryptographic algorithm. This flaw allows an attacker to bypass mandatory integrity protections by supplying a forged ID Token with a deliberately unrecognized alg header parameter. The library intercepts the unsupported state and silently returns True (validation passed), inherently violating fundamental cryptographic design principles and direct OIDC specifications. This issue has been patched in version 1.6.9.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.0024 15th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Partial authlib (authlib): 1.6.9authlib (PyPI): 1.6.9Red Hat: 7 advisoriesRed Hat: 5 fixed, 2 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
authlibauthlibbefore 1.6.91.6.9Patch availableCNA
—authlib (PyPI)before 1.6.91.6.9Patch availableGHSA-m344-f55w-2m6j
  • authlib Vendorauthlib Affected before 1.6.9 Fixed in 1.6.9 Patch available CNA
  • authlib (PyPI) Vendor— Affected before 1.6.9 Fixed in 1.6.9 Patch available GHSA-m344-f55w-2m6j

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:authlib:authlib:*:*:*:*:*:*:*:*before 1.6.9Vulnerableauthlib
  • cpe:2.3:a:authlib:authlib:*:*:*:*:*:*:*:* Versions before 1.6.9 Vulnerable ·authlib

Remediation

  • Fix · CNA authlib (authlib) Fixed in 1.6.9
  • Fix · GHSA-m344-f55w-2m6j authlib (PyPI) Fixed in 1.6.9 Advisory →

Red Hat 7 advisories

  • RHSA-2026:6912 Released 2026-04-07 · Red Hat rating Important
    Red Hat Quay 3.10.20
    • Red Hat Quay 3.10 registry.redhat.io/quay/quay-rhel8
  • RHSA-2026:6720 Released 2026-04-06 · Red Hat rating Important
    Red Hat Quay 3.12.16
    • Red Hat Quay 3.12 registry.redhat.io/quay/quay-rhel8
  • RHSA-2026:6568 Released 2026-04-03 · Red Hat rating Important
    Red Hat Quay 3.15.4
    • Red Hat Quay 3.15 registry.redhat.io/quay/quay-rhel8
Show 4 more Red Hat advisories
  • RHSA-2026:6567 Released 2026-04-03 · Red Hat rating Important
    Red Hat Quay 3.16.3
    • Red Hat Quay 3.16 registry.redhat.io/quay/quay-rhel9
  • RHSA-2026:6497 Released 2026-04-02 · Red Hat rating Important
    Red Hat Quay 3.16.3
    • Red Hat Quay 3.16 registry.redhat.io/quay/quay-rhel9
  • RHSA-2026:6404 Released 2026-04-01 · Red Hat rating Important
    Red Hat Ansible Automation Platform 2.6 Container Release Update
    • Red Hat Ansible Automation Platform 2.6 registry.redhat.io/ansible-automation-platform-26/gateway-rhel9, registry.redhat.io/ansible-automation-platform-26/hub-rhel9, registry.redhat.io/ansible-automation-platform-26/lightspeed-chatbot-rhel9 +2
  • RHSA-2026:6309 Released 2026-03-31 · Red Hat rating Important
    Red Hat Ansible Automation Platform 2.6 Container Release Update
    • Red Hat Ansible Automation Platform 2.6 registry.redhat.io/ansible-automation-platform-26/gateway-rhel9, registry.redhat.io/ansible-automation-platform-26/hub-rhel9, registry.redhat.io/ansible-automation-platform-26/lightspeed-chatbot-rhel9 +2

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Ansible Automation Platform 2AffectedNo fix yet
Red Hat Satellite 6AffectedNo fix yet
Red Hat Ansible Automation Platform 2.6Fixed RHSA-2026:6309
Red Hat Quay 3.10Fixed RHSA-2026:6912
Red Hat Quay 3.12Fixed RHSA-2026:6720
Red Hat Quay 3.15Fixed RHSA-2026:6568
Red Hat Quay 3.16Fixed RHSA-2026:6497, RHSA-2026:6567
Not affected: 7 products
  • Lightspeed Core
  • Red Hat Ansible Automation Platform 2.6
  • Red Hat OpenShift AI (RHOAI)
  • Red Hat Quay 3.10
  • Red Hat Quay 3.12
  • Red Hat Quay 3.15
  • Red Hat Quay 3.16

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-28498
  2. 2026-10-03 Alias added: GHSA-m344-f55w-2m6j

References

Exploit 1

Patch 1

Advisory 1

Other 2

  • TI-2026-22305 Authlib JWS JWK Header Injection: Signature Verification Bypass CVSS 3.1CRITICAL 9.1
  • TI-2026-79518 Authlib fix bypass lets attackers forge HS256 tokens with PEM keys CVSS 3.1CRITICAL 9.1
  • TI-2025-36973 Authlib: JWS/JWT accepts unknown crit headers (RFC violation → possible authz bypass) CVSS 3.1HIGH 7.5
  • TI-2024-25068 lepture Authlib before 1.3.1 has algorithm confusion with asymmetric public keys. CVSS 3.1HIGH 7.5
  • TI-2025-41738 Authlib: 1-click Account Takeover CVSS 3.1HIGH 8.8
  • TI-2026-22754 Authlib Vulnerable to JWE RSA1_5 Bleichenbacher Padding Oracle CVSS 4.0HIGH 8.3
See all 18 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences