What is CVE-2024-35225?

CVE-2024-35225 is a critical-severity vulnerability in Jupyter Server Proxy, classified under Cross-site Scripting. CVSS score: 9.6/10. Published 2024-06-11.

How severe is CVE-2024-35225?

Critical severity. CVSS v3 base score is 9.6 out of 10.

XSS in Jupyter Server Proxy

CVE-2024-35225

Jupyter Server Proxy allows users to run arbitrary external processes alongside their notebook server and provide authenticated web access to them. Versions of 3.x prior to 3.2.4 and 4.x prior to 4.2.0 have a reflected cross-site scripting (XSS) issue. The `/proxy` endpoint accepts a `host` path segment in the format `/proxy/<host>`. When this endpoint is called with an invalid `host` value, `jupyter-server-proxy` replies with a response that includes the value of `host`, without sanitization [2]. A third-party actor can leverage this by sending a phishing link with an invalid `host` value containing custom JavaScript to a user. When the user clicks this phishing link, the browser renders the response of `GET /proxy/<host>`, which runs the custom JavaScript contained in `host` set by the actor. As any arbitrary JavaScript can be run after the user clicks on a phishing link, this issue permits extensive access to the user's JupyterLab instance for an actor. Patches are included in versions 4.2.0 and 3.2.4. As a workaround, server operators who are unable to upgrade can disable the `jupyter-server-proxy` extension.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2024-06-11 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.6 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.004 (36.3th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 36th percentile — 36.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000

Affected products

Jupyter Server Proxy
Jupyterhub Jupyter-Server-Proxy — versions >= 3.0.0, < 3.2.4, >= 4.0.0, < 4.2.0

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2024-35225?: CVE-2024-35225 is a critical-severity vulnerability in Jupyter Server Proxy, classified under Cross-site Scripting. CVSS score: 9.6/10. Published 2024-06-11.
How severe is CVE-2024-35225?: Critical severity. CVSS v3 base score is 9.6 out of 10.