CVE-2026-28490 Details
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.
A cryptographic padding oracle vulnerability exists in the Authlib Python library, specifically in versions prior to 1.6.9. This vulnerability pertains to the JSON Web Encryption (JWE) RSA1_5 key management algorithm, which is registered by Authlib in its default algorithm registry without requiring explicit opt-in. The issue arises because Authlib actively undermines the constant-time Bleichenbacher mitigation that the underlying cryptography library implements correctly. As a result, an attacker can exploit this vulnerability to mount a Bleichenbacher attack, recovering encrypted keys and potentially decrypting JWE payloads or forging new JWE tokens.
Users are advised to update to Authlib version 1.6.9, where this vulnerability has been patched. In this version, the library no longer registers RSA1_5 in the default algorithm registry and restores the constant-time behavior required to prevent the padding oracle vulnerability.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Mar 16, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/authlib/authlib/commit/48b345f29f6c459f11c6a40162b6c0b742ef2e22 | [email protected] | Patch |
| https://github.com/authlib/authlib/releases/tag/v1.6.9 | [email protected] | ProductRelease Notes |
| https://github.com/authlib/authlib/security/advisories/GHSA-7432-952r-cw78 | [email protected] | ExploitMitigationVendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-203 | Observable Discrepancy | [email protected] |
| CWE-327 | Use of a Broken or Risky Cryptographic Algorithm | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| authlib authlib | < 1.6.9 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Mar 17, 2026 | Initial Analysis | [email protected] |
| Mar 16, 2026 | New CVE Received | [email protected] |