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TI-2025-36973 Aliases CVE-2025-59420GHSA-9ggr-2464-2j32

Authlib: JWS/JWT accepts unknown crit headers (RFC violation → possible authz bypass)

Priority HIGH 72CWE-345Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Security bypass
Confidentiality · integrity · availability
None · High · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-345.

Summary

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.4, Authlib’s JWS verification accepts tokens that declare unknown critical header parameters (crit), violating RFC 7515 “must‑understand” semantics. An attacker can craft a signed token with a critical header (for example, bork or cnf) that strict verifiers reject but Authlib accepts. In mixed‑language fleets, this enables split‑brain verification and can lead to policy bypass, replay, or privilege escalation. This issue has been patched in version 1.6.4.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00275 20th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed authlib (authlib): 1.6.4authlib (PyPI): 1.6.4Red Hat: 10 advisories

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
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 1.6.41.6.4Patch availableCNA
—authlib (PyPI)before 1.6.41.6.4Patch availableGHSA-9ggr-2464-2j32
  • authlib Vendorauthlib Affected before 1.6.4 Fixed in 1.6.4 Patch available CNA
  • authlib (PyPI) Vendor— Affected before 1.6.4 Fixed in 1.6.4 Patch available GHSA-9ggr-2464-2j32

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:authlib:authlib:*:*:*:*:*:*:*:*before 1.6.4Vulnerableauthlib
  • cpe:2.3:a:authlib:authlib:*:*:*:*:*:*:*:* Versions before 1.6.4 Vulnerable ·authlib

Remediation

  • Fix · CNA authlib (authlib) Fixed in 1.6.4
  • Fix · GHSA-9ggr-2464-2j32 authlib (PyPI) Fixed in 1.6.4 Advisory →

Red Hat 10 advisories

  • RHSA-2026:4215 Released 2026-03-10 · Red Hat rating Important
    Red Hat Quay 3.14.6
    • Red Hat Quay 3.14 registry.redhat.io/quay/quay-rhel8
  • RHSA-2026:1942 Released 2026-02-04 · Red Hat rating Important
    Red Hat Quay 3.15.3
    • Red Hat Quay 3.15 registry.redhat.io/quay/quay-rhel8
  • RHSA-2025:23176 Released 2025-12-15 · Red Hat rating Important
    Red Hat Quay 3.13.10
    • Red Hat Quay 3.13 registry.redhat.io/quay/quay-builder-rhel8, registry.redhat.io/quay/quay-container-security-operator-rhel8, registry.redhat.io/quay/quay-rhel8
Show 7 more Red Hat advisories
  • RHSA-2025:23064 Released 2025-12-10 · Red Hat rating Important
    Red Hat Quay 3.10.17
    • Red Hat Quay 3.10 registry.redhat.io/quay/quay-builder-rhel8, registry.redhat.io/quay/quay-operator-rhel8, registry.redhat.io/quay/quay-rhel8
  • RHSA-2025:23061 Released 2025-12-10 · Red Hat rating Important
    Red Hat Quay 3.9.17
    • Red Hat Quay 3.9 registry.redhat.io/quay/quay-builder-rhel8, registry.redhat.io/quay/quay-container-security-operator-rhel8, registry.redhat.io/quay/quay-operator-rhel8 +1
  • RHSA-2025:23060 Released 2025-12-10 · Red Hat rating Important
    Red Hat Quay 3.12
    • Red Hat Quay 3.12 registry.redhat.io/quay/quay-builder-rhel8, registry.redhat.io/quay/quay-container-security-operator-rhel8, registry.redhat.io/quay/quay-rhel8
  • RHSA-2025:23059 Released 2025-12-10 · Red Hat rating Important
    Red Hat Quay 3.12
    • Red Hat Quay 3.12 registry.redhat.io/quay/quay-builder-rhel8, registry.redhat.io/quay/quay-container-security-operator-rhel8, registry.redhat.io/quay/quay-rhel8
  • RHSA-2025:23028 Released 2025-12-10 · Red Hat rating Important
    Red Hat Quay 3.12
    • Red Hat Quay 3.12 registry.redhat.io/quay/quay-builder-rhel8, registry.redhat.io/quay/quay-container-security-operator-rhel8, registry.redhat.io/quay/quay-rhel8
  • RHSA-2025:22287 Released 2025-11-27 · Red Hat rating Important
    Red Hat Quay 3.9
    • Red Hat Quay 3.9 registry.redhat.io/quay/quay-operator-rhel8, registry.redhat.io/quay/quay-rhel8
  • RHSA-2025:22182 Released 2025-11-26 · Red Hat rating Important
    Red Hat Quay 3.10.16
    • Red Hat Quay 3.10 registry.redhat.io/quay/quay-operator-rhel8, registry.redhat.io/quay/quay-rhel8

Vendor assessments

Red Hat

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

ProductStatusPlan or fix
Red Hat Quay 3.10Fixed RHSA-2025:22182, RHSA-2025:23064
Red Hat Quay 3.12Fixed RHSA-2025:23028
Red Hat Quay 3.13Fixed RHSA-2025:23176
Red Hat Quay 3.14Fixed RHSA-2026:4215
Red Hat Quay 3.15Fixed RHSA-2026:1942
Red Hat Quay 3.9Fixed RHSA-2025:22287, RHSA-2025:23061
Not affected: 6 products
  • Red Hat Quay 3.10
  • Red Hat Quay 3.12
  • Red Hat Quay 3.13
  • Red Hat Quay 3.14
  • Red Hat Quay 3.15
  • Red Hat Quay 3.9

Timeline

  1. 2026-10-02 Threatist record created from CVE-2025-59420
  2. 2026-10-03 Alias added: GHSA-9ggr-2464-2j32

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-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-2026-22761 Authlib: Fail-Open Cryptographic Verification in OIDC Hash Binding CVSS 4.0HIGH 8.2
  • 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