Affected versions of the jwt-simple package allow users to select what algorithm the server will use to verify a provided JWT. A malicious actor can use this behaviour to arbitrarily modify the contents of a JWT while still passing verification. For the common use case of the JWT, the end result is a complete authentication bypass with minimal effort.

Recommendation

Update to version 0.3.1 or later.

Additionally, be sure to always specify an algorithm in calls to .decode().

References

• https://nvd.nist.gov/vuln/detail/CVE-2016-10555
• hokaccha/node-jwt-simple#16
• hokaccha/node-jwt-simple@957957c
• https://www.npmjs.com/advisories/87
• hokaccha/node-jwt-simple#14
• https://auth0.com/blog/2015/03/31/critical-vulnerabilities-in-json-web-token-libraries/