CVE-2017-11424: Debian Linux

High severity, CVSS 7.5. EPSS: 1.8% chance of exploitation in the next 30 days.

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.

Affected products

• Debian Debian Linux: version 8.0 only; version 9.0 only
• Pyjwt Project Pyjwt: up to and including 1.5.0

Published 2017-08-24. Last modified 2026-06-17.