CVE-2026-42280: Auth0.js SDK Improper Permission Checking Vulnerability
Summary
CVE-2026-42280: Auth.js SDK has Improper Permission Checking. Affects auth0-js versions >= 8.11.0, < 10.0.0. Fixed in 10.0.0. How to fix ↓
Check if this vulnerability affects your application
Upload a manifest or SBOM and we'll show whether you're affected, plus every other risky package in the same scan.
No signup required · Results in about 60 seconds
Background
Auth0.js is a widely used SDK for implementing authentication in web applications. It provides developers with tools to manage user authentication and authorization seamlessly. The SDK supports various authentication flows and integrates with multiple identity providers, making it a popular choice for securing applications. However, a vulnerability has been identified in versions 8.11.0 to 9.32.0, where improper permission checking can lead to unauthorized access to user profile information.
Vulnerability Detail
The vulnerability arises when a specifically crafted invalid ID token is provided to the Auth0.js SDK. Under certain conditions, the SDK may improperly return user profile information using a valid access token, potentially exposing sensitive user data. This issue is particularly concerning for applications that rely on access control rules defined in Auth0 Actions, as it undermines the intended security measures. The vulnerability is classified under CWE-863, which pertains to improper authorization.
How To Fix
Latest published version: 10.3.0 as of 22 Oct 2026
npm install auth0-js@10.3.0Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
10.0.0
This is the first release that contains the fix.
npm install auth0-js@10.0.0Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, ensure that your application implements additional checks on user permissions before displaying sensitive information, even if a valid access token is presented. This can help mitigate the risk until the SDK is updated.
Conclusion
The Auth0.js SDK has a significant vulnerability that can lead to unauthorized access to user profile information under specific conditions. It is crucial for developers using affected versions to upgrade to version 10.0.0 or higher to ensure the security of their applications. Implementing additional permission checks can also help mitigate risks until the upgrade is completed.
See every vulnerability recorded for auth0-js →
FAQ
The vulnerability affects Auth0.js versions between 8.11.0 and 9.32.0.
If exploited, this vulnerability could allow unauthorized users to access sensitive user profile information.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without requiring any signup.
The CVSS score of this vulnerability is 7.1, indicating a high severity level.
The vulnerability was discovered by Quan Le (@aleister1102) and reported responsibly.
References
Related vulnerabilities
Recent vulnerabilities recorded for auth0-js.
