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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

Package

pip python-jwt (pip)

Affected versions

< 3.3.4

Patched versions

3.3.4

Description

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

@davedoesdev davedoesdev published to davedoesdev/python-jwt Sep 21, 2022
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

Severity

Critical

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS score

0.088%
(39th percentile)

Weaknesses

CVE ID

CVE-2022-39227

GHSA ID

GHSA-5p8v-58qm-c7fp

Source code

Credits

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