Input validation error in Debian Linux - CVE-2017-11424
Published: August 24, 2017 / Updated: August 8, 2020
Vulnerability identifier: #VU38428
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2017-11424
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote non-authenticated attacker to manipulate data.
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 software
Debian Linux
Fedora
python-jwt
Fedora
python-jwt
How to mitigate CVE-2017-11424
Install update from vendor's website.
python-jwt - addressed in versions 1.5.3-1.fc26, 1.5.3-1.fc27, 1.6.1-1.el7