CVE-2020-15084: Security Update for express-jwt Library

Published: June 30, 2020

CVE number: CVE-2020-15084

Credit: IST Group

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 or potentially other asymmetric crypto libraries, it may lead to authorization bypass.

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.

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']
});

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