CVE-2023-48223

EIP tracks 2 public exploits for CVE-2023-48223. PoCs published by lucastran05, lucas-tran05.

AI-analyzed exploit summary This repository contains a functional proof-of-concept for CVE-2023-48223, demonstrating an algorithm confusion vulnerability in the `fast-jwt` library. The exploit shows how an attacker can forge a JWT token using HS256 with the public key as the secret, bypassing RS256 verification when the verifier does not enforce a specific algorithm.

fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to version 3.3.2, the fast-jwt library does not properly prevent JWT algorithm confusion for all public key types. The 'publicKeyPemMatcher' in 'fast-jwt/src/crypto.js' does not properly match all common PEM formats for public keys. To exploit this vulnerability, an attacker needs to craft a malicious JWT token containing the HS256 algorithm, signed with the public RSA key of the victim application. This attack will only work if the victim application utilizes a public key containing the `BEGIN RSA PUBLIC KEY` header. Applications using the RS256 algorithm, a public key with a `BEGIN RSA PUBLIC KEY` header, and calling the verify function without explicitly providing an algorithm, are vulnerable to this algorithm confusion attack which allows attackers to sign arbitrary payloads which will be accepted by the verifier. Version 3.3.2 contains a patch for this issue. As a workaround, change line 29 of `blob/master/src/crypto.js` to include a regular expression.