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How the mentioned CVE works:
The vulnerability stems from flawed audience validation in the Auth0-PHP SDK integrated into the Auth0 WordPress plugin. In OAuth 2.0 and OpenID Connect, access tokens and ID tokens serve distinct purposes with specific audience claims. Access tokens target API resources, while ID tokens are for client applications. The “aud” claim in tokens designates the intended recipient. Affected SDK versions improperly validate this claim for access tokens, allowing ID tokens to be mistaken for access tokens. During token verification, the SDK fails to enforce strict audience matching, often skipping checks or incorrectly comparing the “aud” value. This lets tokens with audience claims meant for ID tokens, such as the client ID, be accepted in access token contexts. Attackers can exploit this by obtaining or crafting ID tokens and presenting them to the application as access tokens. The application, due to the validation flaw, trusts these tokens and grants access based on ID token claims, which may lack necessary permissions or scopes. This can lead to authorization bypass, where protected resources are accessed without proper credentials. The issue is exacerbated in multi-tenant setups or where token interchange is feasible. The vulnerability specifically impacts WordPress sites using the Auth0 plugin for authentication, as the underlying SDK processes tokens incorrectly. Without proper validation, sensitive data or functions may be exposed, compromising application security. The flaw is rooted in the token verification logic not differentiating between token types based on audience, leading to improper authorization decisions.
DailyCVE Form:
Platform: Auth0 WordPress
Version: 5.0.0-5.4.0
Vulnerability: Improper Audience Validation
Severity: Moderate
date: 2025-12-17
Prediction: Patch released 2025-12-17
What Undercode Say:
Analytics:
Check installed Auth0 plugin version in WordPress
wp plugin list | grep auth0
Update Auth0 plugin to patched version
wp plugin update auth0 --version=5.5.0
Sample PHP code to verify token audience (proper validation)
$token = getAccessToken();
$expectedAudience = 'https://api.example.com';
if ($token->aud !== $expectedAudience) {
throw new Exception('Invalid audience');
}
How Exploit:
Attackers obtain or forge ID tokens from Auth0 and submit them as access tokens to vulnerable endpoints. The application, due to improper audience validation, accepts these tokens, granting unauthorized access to protected resources or actions.
Protection from this CVE
Upgrade Auth0 WordPress plugin to version 5.5.0 or later, which includes proper audience validation in the Auth0-PHP SDK.
Impact:
Potential authorization bypass, unauthorized data access, and token confusion leading to security breaches in WordPress sites.
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Sources:
Reported By: github.com
Extra Source Hub:
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