python-jwt vulnerable to token forgery with new claims
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: https://github.com/davedoesdev/python-jwt/commit/88ad9e67c53aa5f7c43ec4aa52ed34b7930068c9
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
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | python-jwt | < 3.3.4 | 3.3.4 |
References
- https://github.com/davedoesdev/python-jwt/commit/88ad9e67c53aa5f7c43ec4aa52ed34b7930068c9
- https://github.com/davedoesdev/python-jwt/security/advisories/GHSA-5p8v-58qm-c7fp
- https://nvd.nist.gov/vuln/detail/CVE-2022-39227
- https://github.com/davedoesdev/python-jwt/commit/6c5075469847b9e8b6e5336077d989d77a4d2bf1
- https://github.com/davedoesdev/python-jwt
- https://github.com/pypa/advisory-database/blob/main/vulns/python-jwt/PYSEC-2022-259.yaml
- https://www.vicarius.io/vsociety/posts/authentication-bypass-in-python-jwt
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N- Weakness (CWE)
CWE-290- Platform
- Python (PyPI)
- Package
python-jwt- Disclosed
- 01.09.2022
- Updated
- 11.10.2026 11:19
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2022-259 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-5p8v-58qm-c7fp - CC BY 4.0
Vulnerability history: python-jwt
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
This is the only known vulnerability of this package.
Know which vulnerabilities affect your application
With the DockRay integration and software inventory enabled, DockRay checks reported component versions against known vulnerabilities and notifies you about confirmed matches. Coverage depends on the supported technology and available advisory data.