Forgeable public/private tokens Affecting jwt-simple package, versions <0.3.0



    Attack Complexity High

    Threat Intelligence

    EPSS 0.1% (42nd percentile)
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6.5 medium

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  • Snyk ID npm:jwt-simple:20160804
  • published 31 Oct 2016
  • disclosed 18 Aug 2016
  • credit Theofanis Katsimpas

How to fix?

Upgrade jwt-simple to version 0.3.0 or higher.


'jwt-simple' is a JSON Web Token encode and decode module. Affected versions of this package are vulnerable to an Authentication Bypass attack, due to the "algorithm" not being enforced. Attackers are given the opportunity to choose the algorithm sent to the server and generate signatures with arbitrary contents. The server expects an asymmetric key (RSA) but is sent a symmetric key (HMAC-SHA) with RSA's public key, so instead of going through a key validation process, the server will think the public key is actually an HMAC private key.