Auth0OAuthenticator has an Authentication Bypass via Unverified Email Claims

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.8 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS

• CVE-2026-33175: 0.45% estimated exploitation activity in the next 30 days; percentile 38.82 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary 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 usrnameclaim, this gives users control over their username and the possibility of account takeover. Impact 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. Patches - Upgrade oauthenticator to 17.4 Workarounds - Check emailverified field in an Authenticator.postauthhook function - Do not use email as the username claim - Enforce email verification in auth0

Published by the source

3 Apr 2026, 21:35 UTC

Last modified by the source

10 Sep 2026, 03:51 UTC

Source last checked

26 Oct 2026, 13:40 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-rrvg-cxh4-qhrv

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-rrvg-cxh4-qhrv

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# Patch Next advisory brief: CVE-2026-33175

Advisory: Auth0OAuthenticator has an Authentication Bypass via Unverified Email Claims
IDs: CVE-2026-33175, GHSA-rrvg-cxh4-qhrv
Record: https://patchnext.com/advisories/cve-2026-33175 (revision 2, source checked 26 Oct 2026, 13:40 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: oauthenticator 17.4.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI oauthenticator: affected < 17.4.0; fixed in 17.4.0

## Suggested inspection (read-only)
- `python -m pip show oauthenticator`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on oauthenticator.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-rrvg-cxh4-qhrv (OSV record GHSA-rrvg-cxh4-qhrv lists affected ranges: PyPI oauthenticator >=0 <17.4.0 (fixed))
- Verified: https://github.com/advisories/GHSA-rrvg-cxh4-qhrv (GitHub-reviewed advisory GHSA-rrvg-cxh4-qhrv lists affected ranges: PyPI oauthenticator >=0 <17.4.0)

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