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Improper Verification of Cryptographic Signature

CVE-2026-28802

High
7.7/10

Summary

Authlib is a Python library that builds OAuth and OpenID Connect servers. From version 1.6.5 prior to version 1.6.7, previous tests involving passing a malicious JWT containing alg: none and an empty signature were 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.

  • LOW
  • NETWORK
  • HIGH
  • UNCHANGED
  • NONE
  • NONE
  • HIGH
  • HIGH

CWE-347 - Improper Verification of Cryptographic Signature

A cryptographic protocol is meant to ensure that services are provided in a secure manner. An application with absent or improper verification of cryptographic signatures allows malicious users to feed false messages to valid users or to disclose sensitive data, subverting the goals of the protocol. This can lead to security failures such as false authentication, account hijacking, and privilege escalation.

References

Advisory Timeline

  • Published