CVE-2026-28498

HIGHNVD 7.57.5
EchelonGraph scoreLOW confidence

This high-severity CVE scores 7.5 under NVD CVSS v3. EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: nvd
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.5Exploit: NoneExposed: 0

A fix is available — apply it.

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.

CVSS v3
7.5
EG Score
7.5(low)
EPSS
13.2%
KEV
Not listed

Published

March 16, 2026

Last Modified

July 1, 2026

Advisory Details (10)

Auto-updated Jul 1, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github_release, github, redhat.
redhat Patch Available

cve-details

https://access.redhat.com/security/cve/CVE-2026-28498
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:6912
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:6720
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:6568
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:6567
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:6497
redhat Patch Available
https://access.redhat.com/errata/RHSA-2026:6309
github Patch Available🟡 PoC Available

Fail-Open Cryptographic Verification in Authlib OIDC Hash Binding · Advisory · authlib/authlib · GitHub

https://github.com/authlib/authlib/security/advisories/GHSA-m344-f55w-2m6j
github_release Patch Available

v1.6.9

Patch available: authlib/authlib v1.6.9

https://github.com/authlib/authlib/releases/tag/v1.6.9
github_commit Patch Available

commit b9bb2b25bf8b (authlib/authlib)

Patch available: authlib/authlib v1.6.9 (contains commit b9bb2b25bf8b)

https://github.com/authlib/authlib/commit/b9bb2b25bf8b7e01512d847a95c1749646eaa72b

Vendor Advisories for CVE-2026-28498(7)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(6)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatquay/quay-rhel8:17751691552026-04-07redhat
redhatquay/quay-rhel8:17752530922026-04-06redhat
redhatquay/quay-rhel9:17751692262026-04-03redhat
redhatquay/quay-rhel8:17751692192026-04-03redhat
redhatquay/quay-rhel9:17750694912026-04-02redhat
redhatansible-automation-platform-26/lightspeed-chatbot-rhel9:17744170222026-04-01redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)
PyPI(1)
PackageVulnerable rangeFixed inDependents
authlib0.1 ... 1.6.8 (56 versions)1.6.9—

Weakness Classification(3)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 9× in last 7d / 12× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-06 16:27 UTCEPSS rescore
  2. 2026-07-06 16:27 UTCEPSS rescore
  3. 2026-07-06 02:23 UTCEPSS rescore
  4. 2026-07-06 02:23 UTCEPSS rescore
  5. 2026-07-05 02:30 UTCEPSS rescore
  6. 2026-07-04 06:31 UTCEPSS rescore
  7. 2026-07-01 15:06 UTCEPSS rescore
  8. 2026-06-30 23:22 UTCEPSS rescore
  9. 2026-06-30 23:22 UTCEPSS rescore
  10. 2026-06-30 04:33 UTCEG score recompute
  11. 2026-06-30 04:33 UTCVendor advisory
  12. 2026-06-30 04:31 UTCNVD updatefirst tracked

Frequently asked(5)

What is CVE-2026-28498?
CVE-2026-28498 is a high vulnerability published on March 16, 2026. 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 (verifyhash)…
When was CVE-2026-28498 disclosed?
CVE-2026-28498 was first published in the National Vulnerability Database on March 16, 2026, with the most recent update on July 1, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-28498 actively exploited?
CVE-2026-28498 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 13.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-28498?
CVE-2026-28498 has a CVSS v3 base score of 7.5 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-28498?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-28498, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-28498

Explore →

Is Your Infrastructure Affected by CVE-2026-28498?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs