CVE-2017-11424

Severity: high (CVSS 7.5 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.8% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2017-08-24 · updated 2026-06-17

Description

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 Linux: 8.0, 9.0
jpadilla pyjwt: through 1.5.0

References

http://www.debian.org/security/2017/dsa-3979
https://github.com/jpadilla/pyjwt/pull/277
http://www.debian.org/security/2017/dsa-3979
https://github.com/jpadilla/pyjwt/pull/277

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