Executive Summary

The vulnerability exists in the JOSE Javascript Object Signing and Encryption library versions prior to 0.3.5+1. It allows an unauthenticated remote attacker to forge valid JWS/JWT tokens by exploiting the way the library selects keys for verification.

Specifically, the key selection process mistakenly treats a JSON Web Key (JWK) embedded in the untrusted JOSE header as a valid verification key, even if that key is not present in the application's trusted key store. Since JOSE headers are untrusted input, an attacker can create a token with a malicious public key in the header and sign it with the matching private key, bypassing verification controls.

This flaw allows attackers to forge tokens that appear valid to the application using the affected library.

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Impact Analysis

This vulnerability can impact you by allowing attackers to forge valid JWS/JWT tokens without authentication. This means an attacker can impersonate users or services by creating tokens that the application will accept as legitimate.

The impact is primarily on the integrity of the system, as attackers can bypass signature verification and potentially gain unauthorized access or perform actions with elevated privileges.

There is no impact on confidentiality or availability, but the integrity compromise can lead to serious security breaches.

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Detection Guidance

This vulnerability can be detected by inspecting JWT tokens used in your system to see if they contain a JSON Web Key (jwk) in the JOSE header that is not part of your trusted key store.

You can check logs or token verification failures where tokens with header jwk keys that do not match trusted keys are accepted or rejected.

Since the vulnerability involves accepting untrusted keys from JWT headers, you can use application-level logging or debugging to identify tokens with embedded jwk headers.

There are no specific network commands provided in the resources, but you can use tools like 'jwt-cli' or custom scripts to decode JWT tokens and inspect their headers for the presence of jwk fields.

• Use a JWT decoding tool or command to inspect tokens, for example: jwt decode <token>
• Search application logs for tokens containing 'jwk' in the header.
• Monitor token verification failures related to key mismatches.

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Mitigation Strategies

The primary mitigation is to upgrade the jose library to version 0.3.5+1 or later, where the key resolution logic has been improved to prevent acceptance of untrusted keys embedded in JWT headers.

As an immediate workaround, configure your application to reject any tokens that contain a jwk field in the header unless that jwk matches a key already present in your trusted key store.

This prevents attackers from forging tokens by embedding malicious keys in the header.

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Compliance Impact

This vulnerability allows an unauthenticated remote attacker to forge valid JWS/JWT tokens by exploiting improper verification of cryptographic signatures. Such token forgery can lead to unauthorized access or actions within applications relying on these tokens for authentication and authorization.

Because the integrity of token verification is compromised, applications affected by this vulnerability may fail to enforce proper access controls, potentially leading to violations of security requirements mandated by common standards and regulations such as GDPR and HIPAA.

Specifically, the high integrity impact (CVSS 7.5) indicates that attackers can manipulate data or authentication states, which could result in unauthorized data access or modification, thereby risking non-compliance with data protection and privacy regulations.

Mitigation by upgrading to a patched version or rejecting tokens with untrusted header keys is essential to maintain compliance and secure handling of sensitive data.

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