CVE-2024-35225Network attack vector

Session compromise via unescaped proxy host

Published Jun 11, 2024 · Updated Aug 2, 2024

Reflected XSS in Jupyter Server Proxy 3.x before 3.2.4 and 4.x before 4.2.0 allows remote attackers to run JavaScript via a host path. ProxyHandler writes a disallowed host value directly into its 403 HTML response instead of escaping it, causing embedded markup to execute in the browser. Exploitation requires a JupyterLab user to follow the crafted link; the script then runs in that user's authenticated origin and can access the instance.

CVSS severity9.7
Critical
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reflected XSS in Jupyter Server Proxy 3.x before 3.2.4 and 4.x before 4.2.0 allows remote attackers to run JavaScript via a host path. ProxyHandler writes a disallowed host value directly into its 403 HTML response instead of escaping it, causing embedded markup to execute in the browser. Exploitation requires a JupyterLab user to follow the crafted link; the script then runs in that user's authenticated origin and can access the instance.

The record

CVE
CVE-2024-35225
Published
Jun 11, 2024
Updated
Aug 2, 2024
Vendor
JupyterHub
Product
Jupyter Server Proxy
Classifications
CWE-116, CWE-79, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 11, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 2, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <3.2.4
  2. Affected versionversion=0 <4.2.0
  3. Affected versionversion=3.0.0
  4. Affected versionversion=>= 3.0.0, < 3.2.4
  5. Affected versionversion=4.0.0
  6. Affected versionversion=>= 4.0.0, < 4.2.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

JupyterHub · Jupyter Server Proxyversion=0 <3.2.4; version=0 <4.2.0; version=3.0.0; version=>= 3.0.0, < 3.2.4; version=4.0.0; version=>= 4.0.0, < 4.2.0

Published CVSS scores

9.7GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-116Improper Encoding or Escaping of Output
CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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