CVE-2026-33175

An authentication bypass vulnerability in oauthenticator allows an attacker with an unverified email address on an Auth0 tenant to login to JupyterHub. When email is used as the usrname_claim, this gives users control over their username and the possibility of account takeover.

Workarounds

• Check email_verified field in an Authenticator.post_auth_hook function
• Do not use email as the username claim
• Enforce email verification in auth0

This is an Authentication Bypass Vulnerability. Any Auth0 tenant leveraging the Auth0OAuthenticator mapping the email claim to the JupyterHub username is impacted. By default, Auth0 handles email verification as a user flag, not a hard block to authentication streams. If an attacker can register an account with the Auth0 tenant with an unverified email and knows the email of an existing user on the system, they can authenticate as that user.

The application does not adequately verify the identity of a user, device, or process before granting access. Typical impact: unauthorized access to functions or data reserved for authenticated parties.

CVE-2026-33175 has a CVSS score of 8.8 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (17.4.0); upgrading removes the vulnerable code path.

Kodem intelligence

• Upgrade oauthenticator to 17.4

1. What is CVE-2026-33175? CVE-2026-33175 is a high-severity improper authentication vulnerability in oauthenticator (pip), affecting versions < 17.4.0. It is fixed in 17.4.0. The application does not adequately verify the identity of a user, device, or process before granting access.
2. How severe is CVE-2026-33175? CVE-2026-33175 has a CVSS score of 8.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of oauthenticator are affected by CVE-2026-33175? oauthenticator (pip) versions < 17.4.0 is affected.
4. Is there a fix for CVE-2026-33175? Yes. CVE-2026-33175 is fixed in 17.4.0. Upgrade to this version or later.
5. Is CVE-2026-33175 exploitable, and should I be worried? Whether CVE-2026-33175 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-33175 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-33175? Upgrade oauthenticator to 17.4.0 or later.

Other vulnerabilities in oauthenticator