In PyJWT 1.5.0 and below the `invalid_strings` check in `HMACAlgorithm.prepare_key` does not account for all PEM encoded public keys. Specifically, the PKCS1 PEM encoded format would be allowed because it is prefaced with the string `-----BEGIN RSA PUBLIC KEY-----` which is not accounted for. This enables symmetric/asymmetric key confusion attacks against users using the PKCS1 PEM encoded public keys, which would allow an attacker to craft JWTs from scratch.
Metrics
Affected Vendors & Products
Advisories
Source | ID | Title |
---|---|---|
![]() |
DSA-3979-1 | pyjwt security update |
![]() |
EUVD-2017-0103 | In PyJWT 1.5.0 and below the `invalid_strings` check in `HMACAlgorithm.prepare_key` does not account for all PEM encoded public keys. Specifically, the PKCS1 PEM encoded format would be allowed because it is prefaced with the string `-----BEGIN RSA PUBLIC KEY-----` which is not accounted for. This enables symmetric/asymmetric key confusion attacks against users using the PKCS1 PEM encoded public keys, which would allow an attacker to craft JWTs from scratch. |
![]() |
GHSA-r9jw-mwhq-wp62 | PyJWT vulnerable to key confusion attacks |
![]() |
USN-3407-1 | PyJWT vulnerability |
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
No history.

Status: PUBLISHED
Assigner: duo
Published:
Updated: 2024-08-05T18:12:39.550Z
Reserved: 2017-07-18T00:00:00
Link: CVE-2017-11424

No data.

Status : Deferred
Published: 2017-08-24T16:29:00.197
Modified: 2025-04-20T01:37:25.860
Link: CVE-2017-11424


No data.