CVE-2017-11424 : Exploit Details and Defense Strategies

PyJWT versions 1.5.0 and earlier are vulnerable to a key confusion attack due to incomplete checks on PEM encoded public keys.

Understanding CVE-2017-11424

PyJWT versions 1.5.0 and earlier have a vulnerability that allows attackers to launch key confusion attacks against users utilizing PKCS1 PEM encoded public keys.

What is CVE-2017-11424?

The

HMACAlgorithm.prepare_key

function in PyJWT versions 1.5.0 and earlier lacks a complete check for all PEM encoded public keys, specifically not accounting for the PKCS1 PEM encoded format. This oversight enables attackers to perform symmetric/asymmetric key confusion attacks, potentially leading to the generation of JWTs from scratch.

The Impact of CVE-2017-11424

The vulnerability in PyJWT versions 1.5.0 and earlier can be exploited by attackers to craft JWTs, posing a risk to the integrity and security of systems utilizing PKCS1 PEM encoded public keys.

Technical Details of CVE-2017-11424

PyJWT versions 1.5.0 and earlier are susceptible to key confusion attacks due to incomplete checks on PEM encoded public keys.

Vulnerability Description

The

HMACAlgorithm.prepare_key

function in PyJWT versions 1.5.0 and earlier does not adequately validate all PEM encoded public keys, leaving the PKCS1 PEM encoded format unchecked. This oversight allows for key confusion attacks.

Affected Systems and Versions

Product: PyJWT
Vendor: N/A
Versions affected: 1.5.0 and earlier

Exploitation Mechanism

Attackers can exploit the incomplete check on PEM encoded public keys to launch symmetric/asymmetric key confusion attacks, potentially generating JWTs from scratch.

Mitigation and Prevention

Immediate action and long-term security practices are crucial to mitigate the risks associated with CVE-2017-11424.

Immediate Steps to Take

Update PyJWT to a patched version that addresses the vulnerability.
Avoid using PKCS1 PEM encoded public keys until the issue is resolved.

Long-Term Security Practices

Regularly monitor for security advisories and updates related to PyJWT.
Implement a robust key management strategy to enhance cryptographic security.

Patching and Updates

Apply patches or updates provided by PyJWT to fix the vulnerability and prevent potential key confusion attacks.