In PyJWT 1.5.0 and below the `invalid_strings` check in `HMACAlgorithm.prepare_key` does not account for all PEM encoded public keys. Specifically, the PKCS1 PEM encoded format would be allowed because it is prefaced with the string `-----BEGIN RSA PUBLIC KEY-----` which is not accounted for. This enables symmetric/asymmetric key confusion attacks against users using the PKCS1 PEM encoded public keys, which would allow an attacker to craft JWTs from scratch.

Upgrade to 1.5.3 and also note that 1.5.1 fixed CVE-2017-11424.

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website.
Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

This update for python3-PyJWT fixes the following vulnerability :

  - CVE-2017-11424: Insufficient filtering of PEM encoding     public keys allowed for creation of JWTs from scratch     (boo#1054106, with duplicate CVE-2017-12880)

It was discovered that PyJWT, a Python implementation of JSON Web Token performed insufficient validation of some public key types, which could allow a remote attacker to craft JWTs from scratch.

The remote Ubuntu 16.04 LTS host has packages installed that are affected by a vulnerability as referenced in the USN-3407-1 advisory.

    It was discovered that a vulnerability in PyJWT doesn't check invalid_strings properly for some public     keys. A remote attacker could take advantage of a key confusion to craft JWTs from scratch.

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Severity
105812	Fedora 27 : python-jwt (2017-0cc84101de)	Nessus	Fedora Local Security Checks	high
104082	openSUSE Security Update : python3-PyJWT (openSUSE-2017-1178)	Nessus	SuSE Local Security Checks	high
103439	Fedora 26 : python-jwt (2017-b9f07dfaca)	Nessus	Fedora Local Security Checks	high
103331	Debian DSA-3979-1 : pyjwt - security update	Nessus	Debian Local Security Checks	high
102857	Ubuntu 16.04 LTS : PyJWT vulnerability (USN-3407-1)	Nessus	Ubuntu Local Security Checks	high

Detections

Analytics

CVE-2017-11424

high

Tenable Plugins

high

high

high

high

high