Overview

Versions <=8.5.1 of jsonwebtoken library could be misconfigured so that legacy, insecure key types are used for signature verification. For example, DSA keys could be used with the RS256 algorithm.

Am I affected?

You are affected if you are using an algorithm and a key type other than the combinations mentioned below

Key type	algorithm
ec	ES256, ES384, ES512
rsa	RS256, RS384, RS512, PS256, PS384, PS512
rsa-pss	PS256, PS384, PS512

And for Elliptic Curve algorithms:

alg	Curve
ES256	prime256v1
ES384	secp384r1
ES512	secp521r1

How do I fix it?

Update to version 9.0.0. This version validates for asymmetric key type and algorithm combinations. Please refer to the above mentioned algorithm / key type combinations for the valid secure configuration. After updating to version 9.0.0, If you still intend to continue with signing or verifying tokens using invalid key type/algorithm value combinations, you’ll need to set the allowInvalidAsymmetricKeyTypes option to true in the sign() and/or verify() functions.

Will the fix impact my users?

There will be no impact, if you update to version 9.0.0 and you already use a valid secure combination of key type and algorithm. Otherwise, use the allowInvalidAsymmetricKeyTypes option to true in the sign() and verify() functions to continue usage of invalid key type/algorithm combination in 9.0.0 for legacy compatibility.