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Fencer Vulns
critical 9.1

CVE-2026-28498 json

Authlib: Fail-Open Cryptographic Verification in OIDC Hash Binding

published 2026-03-16 7 mo ago modified 2026-09-10 1 mo ago also EUVD-2026-12482 , GHSA-m344-f55w-2m6j , PYSEC-2026-2117

cvss
9.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 15%
public exploits
0
none known

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.

Patch / fix

  • pypi authlib 1.6.9
  • Red Hat Red Hat Ansible Automation Platform 2.6 1774417022
  • Red Hat Red Hat Quay 3.10 1775169155
  • Red Hat Red Hat Quay 3.12 1775253092
  • Red Hat Red Hat Quay 3.15 1775169219
  • Red Hat Red Hat Quay 3.16 1775069491, 1775169226
  • python-authlib Debian 12 1.2.0-1+deb12u2
  • python-authlib Debian 14 1.6.9-1

debian advisories DEBIAN-CVE-2026-28498

  • python-authlib Ubuntu Pro 22.04 LTS 0.15.5-1ubuntu0.1~esm2
  • python-authlib Ubuntu Pro 24.04 LTS 1.3.0-1ubuntu0.1~esm2
  • python-authlib Ubuntu Pro 26.04 LTS 1.6.7-1ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2026-28498

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • python-Authlib SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Module for Python 3 15 SP7 +1 more 1.3.1-150600.3.17.1

suse advisories SUSE-SU-2026:0975-1

  • python-Authlib openSUSE Leap 16.0 1.5.2-bp160.3.1

opensuse advisories openSUSE-SU-2026:20392-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-28498 updated cvss 9.1

authlib: Authlib: Authentication bypass via forged OpenID Connect ID Tokens

  • Red Hat Ansible Automation Platform 2 ansible-automation-platform-25/lightspeed-chatbot-rhel8 Red Hat Satellite 6 satellite/foreman-mcp-server-rhel9
    affected: no fix available
  • Red Hat Ansible Automation Platform 2.6 ansible-automation-platform-26 1774417022
    fixed: vendor fix RHSA-2026:6309
  • Red Hat Quay 3.10 quay 1775169155
    fixed: vendor fix RHSA-2026:6912
  • Red Hat Quay 3.12 quay 1775253092
    fixed: vendor fix RHSA-2026:6720
  • Red Hat Quay 3.15 quay 1775169219
    fixed: vendor fix RHSA-2026:6568
  • Red Hat Quay 3.16 quay 1775069491, quay 1775169226
    fixed: vendor fix RHSA-2026:6497
  • Red Hat Lightspeed Core lightspeed-core/lightspeed-stack-rhel9 Red Hat Ansible Automation Platform 2.6 ansible-automation-platform 1774648896, ansible-automation-platform 1774648925, ansible-automation-platform-26 1774139204, ansible-automation-platform-26 1774139334, ansible-automation-platform-26 1774153089, ansible-automation-platform-26 1774243862, +22 more
    not affected: vulnerable code not present
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-mlflow-rhel9, rhoai/odh-pipeline-runtime-minimal-cpu-py312-rhel9, rhoai/odh-pipeline-runtime-pytorch-cuda-py312-rhel9, rhoai/odh-pipeline-runtime-pytorch-rocm-py312-rhel9, rhoai/odh-workbench-jupyter-minimal-cpu-py312-rhel9, rhoai/odh-workbench-jupyter-minimal-cuda-py312-rhel9, +13 more
    not affected: component not present
show 1 more
  • Red Hat Quay 3.10 quay 1774885559, quay 1774885579, quay 1774885592, quay 1774885636, quay 1774885638, quay 1774886143, +1 more Red Hat Quay 3.12 quay 1774885546, quay 1774885564, quay 1774885572, quay 1774885604, quay 1774885641, quay 1774886107, +3 more Red Hat Quay 3.15 quay 1774979159, quay 1774979227, quay 1774980222, quay 1774980224, quay 1774984603, quay 1775183105, +3 more Red Hat Quay 3.16 quay 1773781267, quay 1773784956, quay 1773784969, quay 1773784980, quay 1773785008, quay 1773785412, +10 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.24% chance of exploitation in the next 30 days, higher than 15% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/authlib/authlib/security/advisories/GHSA-m344-f55w-2m6j referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 8.2 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
CISA ADP 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CNA 4.0 8.2 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CNA 3.1 9.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected packages

ecosystem package affected fixed in
pypi authlib
<1.6.9
1.6.9

Affected products

  • authlib authlib
  • Red Hat Red Hat Ansible Automation Platform 2.6
  • Red Hat Red Hat Quay 3.10
  • Red Hat Red Hat Quay 3.12
  • Red Hat Red Hat Quay 3.15
  • Red Hat Red Hat Quay 3.16
  • Red Hat Lightspeed Core
  • Red Hat Red Hat Ansible Automation Platform 2
  • Red Hat Red Hat OpenShift AI (RHOAI)
  • Red Hat Red Hat Satellite 6

Classification

Weakness
  • CWE-354 Improper Validation of Integrity Check Value
  • CWE-573 Improper Following of Specification by Caller
  • CWE-325 Missing Cryptographic Step

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.