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TI-2025-38269 Aliases CVE-2025-61920GHSA-pq5p-34cr-23v9

Authlib is vulnerable to Denial of Service via Oversized JOSE Segments

Priority LOW 34CWE-20Published · Updated

Key facts

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

Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-400.

Summary

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.5, Authlib’s JOSE implementation accepts unbounded JWS/JWT header and signature segments. A remote attacker can craft a token whose base64url‑encoded header or signature spans hundreds of megabytes. During verification, Authlib decodes and parses the full input before it is rejected, driving CPU and memory consumption to hostile levels and enabling denial of service. Version 1.6.5 patches the issue. Some temporary workarounds are available. Enforce input size limits before handing tokens to Authlib and/or use application-level throttling to reduce amplification risk.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00638 50th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed authlib (authlib): 1.6.5authlib (PyPI): 1.6.5Red Hat: 9 advisories

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
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 1.6.51.6.5Patch availableCNA
—authlib (PyPI)before 1.6.51.6.5Patch availableGHSA-pq5p-34cr-23v9
  • authlib Vendorauthlib Affected before 1.6.5 Fixed in 1.6.5 Patch available CNA
  • authlib (PyPI) Vendor— Affected before 1.6.5 Fixed in 1.6.5 Patch available GHSA-pq5p-34cr-23v9

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:authlib:authlib:*:*:*:*:*:*:*:*before 1.6.5Vulnerableauthlib
  • cpe:2.3:a:authlib:authlib:*:*:*:*:*:*:*:* Versions before 1.6.5 Vulnerable ·authlib

Remediation

  • Fix · CNA authlib (authlib) Fixed in 1.6.5
  • Fix · GHSA-pq5p-34cr-23v9 authlib (PyPI) Fixed in 1.6.5 Advisory →

Red Hat 9 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-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
  • 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
Show 6 more Red Hat advisories
  • 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 3.9Fixed RHSA-2025:22287, RHSA-2025:23061
Not affected: 5 products
  • Red Hat Quay 3.10
  • Red Hat Quay 3.12
  • Red Hat Quay 3.13
  • Red Hat Quay 3.14
  • Red Hat Quay 3.9

Timeline

  1. 2026-10-02 Threatist record created from CVE-2025-61920
  2. 2026-10-03 Alias added: GHSA-pq5p-34cr-23v9
  3. 2026-10-24 EPSS moved to the 50th–90th percentile

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-2026-22761 Authlib: Fail-Open Cryptographic Verification in OIDC Hash Binding CVSS 4.0HIGH 8.2
See all 18 →

Sources

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