# CVE-2026-33175: OAuthenticator: Authentication Bypass in Auth0OAuthenticator via Unverified Email Claims

> Attackers with unverified Auth0 emails can bypass authentication and take over JupyterHub accounts when email is used as the username claim.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 3 Apr 2026
- **Updated:** 7 Apr 2026
- **Also known as:** CLEANSTART-2026-ZW90347, GHSA-rrvg-cxh4-qhrv, PYSEC-2026-2238

## What is CVE-2026-33175?

CVE-2026-33175 is a high-severity authentication bypass vulnerability in jupyterhub oauthenticator, published on 3 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

OAuthenticator is software that allows OAuth2 identity providers to be plugged in and used with JupyterHub. Prior to version 17.4.0, 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. This issue has been patched in version 17.4.0.

Weakness: CWE-290 (Authentication Bypass by Spoofing), CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2026-33175?

3 open source packages ship an affected version, including oauthenticator. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `oauthenticator` | PyPI | All versions | 17.4.0 |
| `oauthenticator` | PyPI | All versions | 17.4.0 |
| `oauthenticator` | PyPI | All versions | 17.4.0 |

Products: Jupyter Oauthenticator.

## How do I fix CVE-2026-33175?

Upgrade oauthenticator to 17.4.0 or later.

## Is CVE-2026-33175 being exploited?

There is no known exploitation of CVE-2026-33175 in the wild and no public exploit code.

## Other vulnerabilities in jupyterhub oauthenticator

- [CVE-2018-7206](https://insights.sbomify.com/CVE-2018-7206/): JupyterHub OAuthenticator elevation of privilege (high 8.8)
- [CVE-2024-29033](https://insights.sbomify.com/CVE-2024-29033/): GoogleOAuthenticator.hosted_domain incorrectly verifies membership of an Google organization/workspace (high 7.5)
- [CVE-2020-26250](https://insights.sbomify.com/CVE-2020-26250/): Base class whitelist configuration ignored in OAuthenticator (medium 6.3)
- [CVE-2022-31027](https://insights.sbomify.com/CVE-2022-31027/): Authorization Bypass Through User-Controlled Key when using CILogonOAuthenticator in oauthenticator (medium 4.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-33175 and fix it if it is affected.

What it is: CVE-2026-33175 is a high-severity authentication bypass vulnerability in jupyterhub oauthenticator, published on 3 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-33175 in the wild and no public exploit code.

Affected packages and fixed versions:
- oauthenticator (PyPI): affected all versions; fixed in 17.4.0
- oauthenticator (PyPI): affected all versions; fixed in 17.4.0
- oauthenticator (PyPI): affected all versions; fixed in 17.4.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-33175/ (Markdown: https://insights.sbomify.com/CVE-2026-33175/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-33175
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33175
- OSV: https://osv.dev/vulnerability/CVE-2026-33175

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-33175/
Summaries are generated and may contain mistakes; the official description above is the record.