How severe is CVE-2026-28802?

CVE-2026-28802 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-28802 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (34th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-28802?

CVE-2026-28802 affects Authlib. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-28802?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-28802 have an EU (EUVD) identifier?

Yes. CVE-2026-28802 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-10009.

When was CVE-2026-28802 published?

CVE-2026-28802 was published on 2026-03-06 and last updated on 2026-07-01.

CVE-2026-28802

CVE-2026-28802 is a critical-severity vulnerability in Authlib with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-347.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v4: 7.7
EPSS exploit prediction: 0% (34th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-10009
Weakness: CWE-347
Affected product: Authlib
Published: 2026-03-06
Last modified: 2026-07-01

Description

Authlib is a Python library which builds OAuth and OpenID Connect servers. From version 1.6.5 to before version 1.6.7, previous tests involving passing a malicious JWT containing alg: none and an empty signature was passing the signature verification step without any changes to the application code when a failure was expected.. This issue has been patched in version 1.6.7.

Frequently asked questions

What is CVE-2026-28802?: Authlib is a Python library which builds OAuth and OpenID Connect servers. From version 1.6.5 to before version 1.6.7, previous tests involving passing a malicious JWT containing alg: none and an empty signature was passing the signature verification step without any changes to the application code when a failure was expected.. This issue has been patched in version 1.6.7.
How severe is CVE-2026-28802?: CVE-2026-28802 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-28802 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (34th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-28802?: CVE-2026-28802 affects Authlib. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-28802?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-28802 have an EU (EUVD) identifier?: Yes. CVE-2026-28802 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-10009.
When was CVE-2026-28802 published?: CVE-2026-28802 was published on 2026-03-06 and last updated on 2026-07-01.

References

Affected products (1)

cpe:2.3:a:authlib:authlib:*:*:*:*:*:*:*:*

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