python-jwt vulnerable to token forgery with new claims
Critical severity
GitHub Reviewed
Published
Sep 21, 2022
in
davedoesdev/python-jwt
•
Updated Aug 9, 2024
Description
Published to the GitHub Advisory Database
Sep 21, 2022
Reviewed
Sep 21, 2022
Published by the National Vulnerability Database
Sep 23, 2022
Last updated
Aug 9, 2024
Impact
An attacker who obtains a JWT can arbitrarily forge its contents without knowing the secret key. Depending on the application, this may for example enable the attacker to spoof other user's identities, hijack their sessions, or bypass authentication.
Patches
Users should upgrade to version 3.3.4
Fixed by: davedoesdev/python-jwt@88ad9e6
Workarounds
None
References
Found by Tom Tervoort
https://github.com/pypa/advisory-database/blob/main/vulns/python-jwt/PYSEC-2022-259.yaml
More information
The vulnerability allows an attacker, who possesses a single valid JWT, to create a new token with forged claims that the verify_jwt function will accept as valid.
The issue is caused by an inconsistency between the JWT parsers used by python-jwt and its dependency jwcrypto. By mixing compact and JSON representations, an attacker can trick jwcrypto of parsing different claims than those over which a signature is validated by jwcrypto.
Testing the fix has been added as an automated unit test to python-jwt.
If you have any questions or comments about this advisory, please open an issue in python-jwt
References