How severe is CVE-2024-35225?

CVE-2024-35225 has a CVSS score of 9.6/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2024-35225?

CVE-2024-35225 affects the following packages: jupyter-server-proxy (PyPI), jupyter-server-proxy (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2024-35225?

Update jupyter-server-proxy to 3.2.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-35225 is resolved across your whole dependency graph.

How do I detect CVE-2024-35225 in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for jupyter-server-proxy, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2024-35225 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2024-35225 actively exploited in the wild?

No public exploit code has been indexed for CVE-2024-35225 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2024-35225?

CVE-2024-35225 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 39th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2024-35225?

CVE-2024-35225 is classified as Cross-site Scripting (XSS) (CWE-79), CWE-116 (CWE-116). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2024-35225 published, and has it been updated?

CVE-2024-35225 was published on June 11, 2024 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍

🐍 PyPI

Not in CISA KEV

CRITICAL severity

CVE-2024-35225 — jupyter-server-proxy

CRITICALFix: jupyterhub/jupyter-server-proxy@7abc9dc

CVE-2024-35225 is a critical-severity (CVSS 9.6) Cross-site Scripting (XSS) vulnerability in jupyter-server-proxy. A fix is available for jupyter-server-proxy — see the affected versions and patch details below.

Jupyter Server Proxy has a reflected XSS issue in host parameter

Also known asGHSA-fvcq-4x64-hqxrPYSEC-2024-236

Published

Jun 11, 2024

Updated

Oct 28, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2024-35225.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs39th percentile — riskier than 39% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected

🐍jupyter-server-proxy🐍jupyter-server-proxy

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

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

Patches

The patches are included in ==4.2.0 and ==3.2.4.

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

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`jupyter-server-proxy`	≥ 3.0.0&&< 3.2.4	3.2.4`pip install --upgrade 'jupyter-server-proxy==3.2.4'`
🐍PyPI	`jupyter-server-proxy`	≥ 4.0.0&&< 4.2.0	4.2.0`pip install --upgrade 'jupyter-server-proxy==4.2.0'`

Affected Products

1 product · 2 configurations

Application

jupyter server proxyjupyter

≥ 4.1.2 && < 4.2.0

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for jupyter-server-proxy, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update jupyter-server-proxy to 3.2.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-35225 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

### 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