CVE-2020-26250 : What You Need to Know

OAuthenticator is an OAuth login mechanism for JupyterHub. In oauthenticator from version 0.12.0 and before 0.12.2, the deprecated configuration

Authenticator.whitelist

is ignored, potentially allowing all authenticated users access.

Understanding CVE-2020-26250

This CVE highlights a vulnerability in OAuthenticator that could lead to incorrect authorization due to the mishandling of the whitelist configuration.

What is CVE-2020-26250?

OAuthenticator, used for OAuth login in JupyterHub, fails to enforce the whitelist configuration properly, potentially granting unauthorized access to all authenticated users.

The Impact of CVE-2020-26250

The vulnerability can result in unauthorized access to resources by allowing all authenticated users, bypassing intended restrictions.

Technical Details of CVE-2020-26250

OAuthenticator's mishandling of the whitelist configuration can have significant security implications.

Vulnerability Description

OAuthenticator versions 0.12.0 to 0.12.1 ignore the

Authenticator.whitelist

configuration, potentially allowing all authenticated users access.

Affected Systems and Versions

Product: oauthenticator
Vendor: jupyterhub
Versions affected: >= 0.12.0, < 0.12.2

Exploitation Mechanism

The deprecated whitelist configuration is not properly enforced, leading to all authenticated users being allowed access.

Mitigation and Prevention

It is crucial to take immediate steps to address and prevent exploitation of this vulnerability.

Immediate Steps to Take

Update OAuthenticator to version 0.12.2 to mitigate the vulnerability.
Replace deprecated

c.Authenticator.whitelist

with

c.Authenticator.allowed_users

.
Delete any unauthorized users via the API or admin interface.

Long-Term Security Practices

Regularly review and update authentication configurations.
Implement group or team-based restrictions for better access control.

Patching and Updates

Stay informed about security advisories and update OAuthenticator promptly to the latest version.