jsonwebtoken's insecure implementation of key retrieval function could lead to Forgeable Public/Private Tokens from RSA to HMAC

Overview

Versions <=8.5.1 of jsonwebtoken library can be misconfigured so that passing a poorly implemented key retrieval function (referring to the secretOrPublicKey argument from the readme link) will result in incorrect verification of tokens. There is a possibility of using a different algorithm and key combination in verification than the one that was used to sign the tokens. Specifically, tokens signed with an asymmetric public key could be verified with a symmetric HS256 algorithm. This can lead to successful validation of forged tokens.

Am I affected?

You will be affected if your application is supporting usage of both symmetric key and asymmetric key in jwt.verify() implementation with the same key retrieval function.

How do I fix it?

Update to version 9.0.0.

Will the fix impact my users?

There is no impact for end users