CVE-2021-41106 Explained : Impact and Mitigation

JWT library versions prior to 3.4.6, 4.0.4, and 4.1.5 are affected by a vulnerability related to file reference keys, leading to incorrect hashes on HMAC algorithms.

Understanding CVE-2021-41106

What is CVE-2021-41106?

JSON Web Token (JWT) library versions prior to 3.4.6, 4.0.4, and 4.1.5 have a vulnerability where HMAC-based algorithms combined with certain key types may generate incorrect hashes, impacting data authenticity verification.

The Impact of CVE-2021-41106

This vulnerability allows for potential incorrect hashing, affecting the security and trustworthiness of tokens issued or validated using HMAC-based algorithms in vulnerable versions.

Technical Details of CVE-2021-41106

Vulnerability Description

The issue arises from the improper use of file path as hashing key instead of contents when using specific key types. This can lead users to believe that token operations are functioning correctly.

Affected Systems and Versions

Affected versions: >= 3.4.0, < 3.4.6, >= 4.0.0, < 4.0.4, >= 4.1.0, < 4.1.5

Exploitation Mechanism

Attack Complexity: Low
Attack Vector: Local
Privileges Required: Low
User Interaction: None
Scope: Unchanged
CVSS Score: 4.4 (Medium)

Mitigation and Prevention

Immediate Steps to Take

Upgrade JWT library to versions 3.4.6, 4.0.4, or 4.1.5
Replace

Lcobucci\JWT\Signer\Key\LocalFileReference

with

Lcobucci\JWT\Signer\Key\InMemory

Use

Lcobucci\JWT\Signer\Key\InMemory

for key instances

Long-Term Security Practices

Regularly update security libraries and dependencies
Conduct security audits and code reviews

Patching and Updates

Implement the patched versions (3.4.6, 4.0.4, 4.1.5) with corrected hashing mechanisms