Authlib: Fail-Open Cryptographic Verification in OIDC Hash Binding
Summary
| CVE | CVE-2026-28498 |
|---|---|
| State | PUBLISHED |
| Assigner | GitHub_M |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-03-16 18:16:07 UTC |
| Updated | 2026-07-01 13:16:55 UTC |
| Description | 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. |
Risk And Classification
Primary CVSS: v4.0 8.2 HIGH from [email protected]
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
EPSS: 0.002260000 probability, percentile 0.132170000 (date 2026-07-02)
Problem Types: CWE-354 | CWE-573 | CWE-325 | CWE-354 CWE-354: Improper Validation of Integrity Check Value | CWE-573 CWE-573: Improper Following of Specification by Caller | CWE-325 Missing Cryptographic Step
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | [email protected] | Secondary | 8.2 | HIGH | 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/C... |
| 4.0 | CNA | DECLARED | 8.2 | HIGH | 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 |
| 3.1 | [email protected] | Primary | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N |
| 3.1 | ADP | CVSS | 9.1 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |
| 3.1 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | Secondary | 9.1 | CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |
CVSS v4.0 Breakdown
Attack Vector
NetworkAttack Complexity
HighAttack Requirements
PresentPrivileges Required
NoneUser Interaction
NoneConfidentiality
NoneIntegrity
HighAvailability
NoneSub Conf.
NoneSub Integrity
NoneSub Availability
NoneCVSS: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
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
NoneUser Interaction
NoneScope
UnchangedConfidentiality
NoneIntegrity
HighAvailability
NoneCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD Known Affected Configurations (CPE 2.3)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Authlib | Authlib | affected < 1.6.9 | Not specified |
| ADP | Red Hat | Red Hat Ansible Automation Platform 2.6 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Quay 3.10 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Quay 3.12 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Quay 3.15 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Quay 3.16 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Ansible Automation Platform 2 | Not specified | Not specified |
| ADP | Red Hat | Red Hat Satellite 6 | Not specified | Not specified |
| ADP | Red Hat | Lightspeed Core | Not specified | Not specified |
| ADP | Red Hat | Red Hat OpenShift AI RHOAI | Not specified | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/authlib/authlib/releases/tag/v1.6.9 | [email protected] | github.com | Product, Release Notes |
| access.redhat.com/errata/RHSA-2026:6720 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:6568 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| bugzilla.redhat.com/show_bug.cgi | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | bugzilla.redhat.com | |
| access.redhat.com/errata/RHSA-2026:6309 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:6912 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:6567 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-28498.json | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | security.access.redhat.com | |
| github.com/authlib/authlib/commit/b9bb2b25bf8b7e01512d847a95c1749646eaa72b | [email protected] | github.com | Patch |
| github.com/authlib/authlib/security/advisories/GHSA-m344-f55w-2m6j | [email protected] | github.com | Exploit, Mitigation, Vendor Advisory |
| access.redhat.com/security/cve/CVE-2026-28498 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:6497 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| ADP | 2026-03-16T19:02:00.128Z | Reported to Red Hat. |
| ADP | 2026-03-16T18:03:28.821Z | Made public. |
Solutions
ADP: RHSA-2026:6309: Red Hat Ansible Automation Platform 2.6
ADP: RHSA-2026:6912: Red Hat Quay 3.10
ADP: RHSA-2026:6720: Red Hat Quay 3.12
ADP: RHSA-2026:6568: Red Hat Quay 3.15
ADP: RHSA-2026:6497: Red Hat Quay 3.16
ADP: RHSA-2026:6567: Red Hat Quay 3.16
There are currently no legacy QID mappings associated with this CVE.