Summary
Jupyter Server Proxy has a reflected XSS issue in host parameter
Workarounds
Server operators who are unable to upgrade can disable the jupyter-server-proxy extension with:
jupyter server extension disable jupyter-server-proxy
References
[1] : https://github.com/jupyterhub/jupyter-server-proxy/
[2] : https://github.com/jupyterhub/jupyter-server-proxy/blob/62a290f08750f7ae55a0c29ca339c9a39a7b2a7b/jupyter_server_proxy/handlers.py#L328
Impact
There is a reflected cross-site scripting (XSS) issue in jupyter-server-proxy[1]. 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. This issue exists in the latest release of jupyter-server-proxy, currently v4.1.2.
Impacted versions: >=3.0.0,<=4.1.2
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
CVE-2024-35225 has a CVSS score of 9.6 (Critical). The vector is network-reachable, no privileges required, and user interaction required. 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 (3.2.4, 4.2.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
The patches are included in ==4.2.0 and ==3.2.4.
Frequently Asked Questions
- What is CVE-2024-35225? CVE-2024-35225 is a critical-severity cross-site scripting (XSS) vulnerability in jupyter-server-proxy (pip), affecting versions >= 3.0.0, < 3.2.4. It is fixed in 3.2.4, 4.2.0. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- How severe is CVE-2024-35225? CVE-2024-35225 has a CVSS score of 9.6 (Critical). 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.
- Which versions of jupyter-server-proxy are affected by CVE-2024-35225? jupyter-server-proxy (pip) versions >= 3.0.0, < 3.2.4 is affected.
- Is there a fix for CVE-2024-35225? Yes. CVE-2024-35225 is fixed in 3.2.4, 4.2.0. Upgrade to this version or later.
- Is CVE-2024-35225 exploitable, and should I be worried? Whether CVE-2024-35225 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
- What actually determines whether CVE-2024-35225 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.
- How do I fix CVE-2024-35225?
- Upgrade
jupyter-server-proxyto 3.2.4 or later - Upgrade
jupyter-server-proxyto 4.2.0 or later
- Upgrade