title: jsonwebtoken's insecure implementation of key retrieval function could lead to Forgeable Public/Private Tokens from RSA to HMAC
description: jsonwebtoken is an implementation of JSON Web Tokens. 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, other 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. If your application is supporting usage of both symmetric key and asymmetric key in jwt.verify() implementation with the same key retrieval function. This issue has been patched, please update to version 9.0.0.
problem types: CWE-287: Improper Authentication
affected:
{
vendor: auth0
product: node-jsonwebtoken
versions:
version: <= 8.5.1, status: affected
}
metrics:
cvssV3_1: [
attackComplexity: HIGH
attackVector: NETWORK
availabilityImpact: LOW
baseScore: 5
baseSeverity: MEDIUM
confidentialityImpact: LOW
integrityImpact: LOW
privilegesRequired: LOW
scope: UNCHANGED
userInteraction: NONE
vectorString: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L
version: 3.1
]