Date: Tue, 31 Mar 2015 22:53:52 -0700 From: "Jeremy Spilman" <jeremy@...link.co> To: "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com> Subject: Signature Bypass in several JSON Web Token Libraries (CVEs Needed?) Tim McLean discovered two serious (related) vulnerabilities common to several widely used JSON Web Token (JSW) libraries which he wrote about here  a month ago, and again today here . A JWT is base64 encoded header, payload, and signature, where the header specifies the signature algorithm and an expiration timestamp. The validation libraries running server side provide APIs such as; verify(string token, string secretKey) The two critical bugs; - Even when a secretKey was provided to the API, if the data in 'token' decoded to a header specifying a signature algorithm of *none*, the API would still return success. Meaning an attacker could just strip the signature, change the header, and bypass the signature validation server-side. - If the secretKey was expected to be a RSA public key, but the attacker changed the header to indicate a signature algorithm of HMAC, the RSA public key would be used as the signing secret. Effected libraries include but probably not limited to: namshi-jose: https://github.com/namshi/jose/commit/127b4415e66d89b1fcfb5a07933db0b5ff5cd636 python-jwt: https://github.com/davedoesdev/python-jwt/commit/5ddb71b2ed5785c329b761e45a246996a1dd9cab node-jsonwebtoken: https://github.com/auth0/node-jsonwebtoken/commit/1bb584bc382295eeb7ee8c4452a673a77a68b687 pyjwt: https://github.com/jpadilla/pyjwt/commit/88a9fc56bdc6c870aa6af93bda401414a217db2a php-jwt: Not yet patched? jsjwt: Not yet patched? I think these are all (possibly independently) CVE worthy... I requested Tim file CVEs here , but I haven't seen any to-date. I'm not sure about requesting CVEs on someone else's work, I'm just an interested bystander here.  - https://www.timmclean.net/2015/02/25/jwt-alg-none.html  - https://auth0.com/blog/2015/03/31/critical-vulnerabilities-in-json-web-token-libraries/  - https://news.ycombinator.com/item?id=9111049
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