Overview

Versions before and including 5.3.3, we are not enforcing the algorithms entry to be specified in the configuration.
When algorithms is not specified in the configuration, with the combination of jwks-rsa, it may lead to authorization bypass.

Am I affected?

You are affected by this vulnerability if all of the following conditions apply:

You are using express-jwt
AND
You do not have algorithms configured in your express-jwt configuration.
AND
You are using libraries such as jwks-rsa as the secret.

How to fix that?

Specify algorithms in the express-jwt configuration. The following is an example of a proper configuration

const checkJwt = jwt({
  secret: jwksRsa.expressJwtSecret({
    rateLimit: true,
    jwksRequestsPerMinute: 5,
    jwksUri: `https://${DOMAIN}/.well-known/jwks.json`
  }),
  // Validate the audience and the issuer.
  audience: process.env.AUDIENCE,
  issuer: `https://${DOMAIN}/`,
  // restrict allowed algorithms
  algorithms: ['RS256']
}); 

Will this update impact my users?

The fix provided in patch will not affect your users if you specified the algorithms allowed. The patch now makes algorithms a required configuration.

Credit

IST Group