Vulnerability · Published Apr 3, 2026 · Assigned by GitHub_M

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

High 8.8

In plain English

A high-severity improper authentication in oauthenticator from jupyterhub. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 39% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.8High

Exploit odds (30 days)0.4%top 61.1% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
PyPI	oauthenticator	17.4.0	GHSA-rrvg-cxh4-qhrv
PyPI	oauthenticator	17.4.0	PYSEC-2026-2238

Affected products (as reported)

Vendor	Product	Versions
jupyterhub	oauthenticator	< 17.4.0

Weakness: CWE-287, CWE-290 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

References

https://github.com/jupyterhub/oauthenticator/security/advisories/GHSA-rrvg-cxh4-qhrv x_refsource_CONFIRM
https://github.com/jupyterhub/oauthenticator/commit/f0c7002dc36e41efae0f674033cf7888a21d96f9 x_refsource_MISC
https://github.com/jupyterhub/oauthenticator/releases/tag/17.4.0 x_refsource_MISC