security security_error ai_generated true

JWT verification failed: algorithm "none" is not allowed

ID: security/jwt-none-algorithm

Also available as: JSON · Markdown
90%Fix Rate
88%Confidence
3Evidence
2023-01-01First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
any active — — —

Root Cause

JWT "none" algorithm attack bypasses signature verification.

generic

Workarounds

  1. 95% success Explicitly specify allowed algorithms in verification 
    jwt.decode(token, key, algorithms=["RS256"])
  2. 88% success Use a JWT library that rejects "none" by default 
    Most modern libraries reject none; ensure you are on latest version

Dead Ends

Common approaches that don't work:

  1. Accept any algorithm the token specifies 95% fail

    Allows attacker to switch from RS256 to HS256 using public key as secret.

  2. Only check token expiry without verifying signature 90% fail

    Unsigned tokens can be forged with any claims.