External risk intelligence

joaquimserafim json-web-token JWT Algorithm Confusion Vulnerability

CVE advisorySeverity: HIGH (CVSS 7.5)

CVE-2023-48238

A vulnerability in a JavaScript library for JSON Web Tokens could allow an attacker to forge tokens by tricking the library into using an incorrect algorithm for signature verification. This may lead to unauthorized access or actions if the library is used in applications relying on JWTs for authentication or authoriza

3Halo Surface Signal

Joaquimserafim Json Web Token

before 3.1.1

External exposure likelihood

Halo Surface Signal score for CVE-2023-48238

This is a JavaScript library used by developers within applications to process JWTs. While libraries are integrated into internet-facing web applications and APIs, the vulnerability exists at the dependency level rather than being an inherent, standalone network-exposed service, appliance, or gateway.

PCI scan relevance

PCI Relevance for CVE-2023-48238

Yes

CVE-2023-48238 — Halo PCI Relevance: Yes. Under typical PCI ASV external scan criteria, this issue may be flagged for scan prioritization.

This CVE involves a JWT algorithm confusion attack that can be exploited remotely and without authentication, potentially leading to an authentication bypass, which is a PCI automatic fail condition.

Scan-prioritization guidance only—not a PCI DSS certification or ASV attestation.

Horizon Alert

Summary of the vulnerability and why it matters

This advisory concerns a vulnerability in a JavaScript library used for handling JSON Web Tokens (JWT). The issue allows an attacker to potentially forge tokens, which could lead to unauthorized access or actions if the library is used in applications that rely on JWTs for authentication or authorization. The main concern is confirming whether this specific library is in use and if the affected configurations are present.

Attackers could forge authentication tokens.
Impacts systems using token-based authorization.
Confirm library use and exposure.

Attack Path

How an attacker could exploit the issue

An attacker could exploit this vulnerability by sending a specially crafted JSON Web Token (JWT) to an application that uses a vulnerable version of the `json-web-token` library. If the application is configured to use the RS256 algorithm for signature verification, the attacker can trick the library into using the HS256 algorithm instead. This would allow the attacker to forge a valid signature using the victim application's public RSA key, potentially leading to unauthorized access or data manipulation.

Requires network access to the vulnerable application.
Triggered by processing a malicious JWT.
Allows unauthorized data modification.

Live Threat

Current exploitation, exposure, and threat context

When using the RS256 algorithm, this vulnerability could allow an attacker to forge JWT tokens. This occurs because the library improperly trusts the algorithm specified within an unverified token, potentially leading to unauthorized actions.

Compromised JWT integrity.
Forged token sent to application.
Unauthorized access may occur.

Priority actions

Operational Fix

Recommended remediation, mitigation, and detection steps

The `joaquimserafim/json-web-token` library is a component that developers integrate into applications, making application owners and platform teams most likely responsible for its management. The initial practical step is to identify all applications utilizing this library, confirm their exposure and business criticality, and then assign ownership for remediation planning.

Application owners should manage this issue.
Verify all application integrations of the library.
Plan updates or mitigate risk.

Frequently asked questions

What is the joaquimserafim json-web-token library used for?

This JavaScript library is a tool developers integrate into Node.js applications to process JSON Web Tokens. These tokens are compact, URL-safe objects used to securely transfer claims or identity information between parties, often serving as the foundation for authentication and authorization in modern web services and APIs.

How does CVE-2023-48238 cause a security weakness?

This vulnerability is an algorithm confusion flaw, classified as CWE-345. It occurs because the library trusts the cryptographic algorithm defined inside an incoming token before verifying that token's signature. By misidentifying the required method, the library can be tricked into accepting a maliciously crafted token as authentic, bypassing intended security checks.

Does any specific configuration prevent this JWT attack?

The attack path relies on the application being configured to use the RS256 algorithm for token verification. If your application does not use RS256, or if you have already updated to version 4.0.0 or later, this specific vulnerability cannot be triggered in the way described.

Is my application vulnerable to this JWT issue?

Halo Surface Signal notes that because this is a library integrated into custom software, it is not a standalone appliance. Your relevance depends on whether your internet-facing web applications or internal APIs rely on this specific library and version. You must check your dependency manifests to confirm if your code integrates the affected versions.

What should I do if my application uses this library?

The primary response is to update the joaquimserafim/json-web-token dependency to version 4.0.0 or higher. Begin by auditing your software project files to identify where this library is imported, verify the currently installed version, and coordinate with your development team to perform the dependency update and subsequent testing.

References

Written by Nicholas Merritt

External-surface CVE analysis and Halo Surface Signal prioritization for Halo Threat Intelligence.