CVE-2022-29217

PyJWT allows an attacker to choose the signing algorithm

• CVSS 7.5
• CWE-327 Use of a Broken or Risky Cryptographic Algorithm
• Input Validation and Sanitization
• Remote

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

CVE-2022-29217

CWE

CWE-327 Use of a Broken or Risky Cryptographic Algorithm

CVSS base score

7.5

Published

2022-05-24

OWASP

A06 Vulnerable and Outdated Components

Orthogonal defect classification

Checking

Code defect classification

Missing Check

Category

Input Validation and Sanitization

Subcategory

Insecure Parsing or Deserialization

Accessibility scope

Remote

Impact

Unauthorized Access

Fixed by upgrading

Yes

Solution

Upgrade to PyJWT version 2.4.0 or higher.

import jwt

SECRET_KEY = 'your_secret_key'

token = 'your_jwt_token_here'

try:
    decoded_token = jwt.decode(token, SECRET_KEY)
    print(decoded_token)
except jwt.InvalidTokenError as e:
    print(f"Invalid token: {e}")

import jwt

SECRET_KEY = 'your_secret_key'

token = 'your_jwt_token_here'

try:
    decoded_token = jwt.decode(token, SECRET_KEY, algorithms=['HS256'])
    print(decoded_token)
except jwt.InvalidTokenError as e:
    print(f"Invalid token: {e}")

@misc{vaitp:cve202229217,
  title        = {{PyJWT allows an attacker to choose the signing algorithm}},
  author       = {Bogaerts, Fr\'ed\'eric and Ivaki, Naghmeh and Fonseca, Jos\'e},
  year         = {2022},
  note         = {VAITP Python Vulnerability Dataset, entry CVE-2022-29217},
  howpublished = {\url{https://netpack.pt/vaitp/vulnerability/CVE-2022-29217/}}
}