How severe is CVE-2026-28490?

CVE-2026-28490 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity low, and availability none.

Is CVE-2026-28490 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (4th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-28490?

CVE-2026-28490 affects Authlib. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-28490?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-28490 have an EU (EUVD) identifier?

Yes. CVE-2026-28490 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-12480.

When was CVE-2026-28490 published?

CVE-2026-28490 was published on 2026-03-16 and last updated on 2026-06-17.

CVE-2026-28490

CVE-2026-28490 is a medium-severity vulnerability in Authlib with a CVSS 3.x base score of 6.5. 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-203.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v4: 8.3
EPSS exploit prediction: 0% (4th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-12480
Weakness: CWE-203
Affected product: Authlib
Published: 2026-03-16
Last modified: 2026-06-17

Description

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a cryptographic padding oracle vulnerability was identified in the Authlib Python library concerning the implementation of the JSON Web Encryption (JWE) RSA1_5 key management algorithm. Authlib registers RSA1_5 in its default algorithm registry without requiring explicit opt-in, and actively destroys the constant-time Bleichenbacher mitigation that the underlying cryptography library implements correctly. This issue has been patched in version 1.6.9.

Frequently asked questions

What is CVE-2026-28490?: Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.9, a cryptographic padding oracle vulnerability was identified in the Authlib Python library concerning the implementation of the JSON Web Encryption (JWE) RSA1_5 key management algorithm. Authlib registers RSA1_5 in its default algorithm registry without requiring explicit opt-in, and actively destroys the constant-time Bleichenbacher mitigation that the underlying cryptography library implements correctly. This issue has been patched in version 1.6.9.
How severe is CVE-2026-28490?: CVE-2026-28490 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity low, and availability none.
Is CVE-2026-28490 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (4th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-28490?: CVE-2026-28490 affects Authlib. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-28490?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-28490 have an EU (EUVD) identifier?: Yes. CVE-2026-28490 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-12480.
When was CVE-2026-28490 published?: CVE-2026-28490 was published on 2026-03-16 and last updated on 2026-06-17.

References

Affected products (1)

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

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