CVE-2020-26275: Jupyter server Jupyter Server Open Redirect Vulnerability Vulnerability

MODERATE
Advisory Identifier: GHSA-9f66-54xg-pc2c
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CVSS 6.1
CWE-601
Published
Advisory Summary

CVE-2020-26275 is a MODERATE (CVSS 6.1) jupyter server open redirect vulnerability vulnerability (CWE-601: URL Redirection to Untrusted Site ('Open Redirect')) affecting Jupyter server libraries in the PyPI ecosystem. The issue involves jupyter server open redirect vulnerability. Remediation is available by upgrading affected packages to version 1.1.1.

CVE-2020-26275 at a Glance

CVE Identifier CVE-2020-26275
GHSA Identifier GHSA-9f66-54xg-pc2c
Severity MODERATE
CVSS v3.1 Base Score 6.1
CWE Classification CWE-601: URL Redirection to Untrusted Site ('Open Redirect')
Affected Product Jupyter server
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 6.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Changed (S:C)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2020-26275

To remediate this vulnerability, upgrade all affected Jupyter server dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

jupyter-server fixed: 1.1.1 
pip install jupyter-server>=1.1.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show jupyter-server

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2020-26275, inspect your installed packages using pip:

pip show jupyter-server

Analyze the terminal output to locate any version of Jupyter server in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.1.1), your application is affected.

Note: The pip show jupyter-server command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-601: URL Redirection to Untrusted Site ('Open Redirect'), where the web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect. In Jupyter server, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact _What kind of vulnerability is it? Who is impacted?_ Open redirect vulnerability - a maliciously crafted link to a jupyter server could redirect the browser to a different website. All jupyter servers running without a base_url prefix are technically affected, however, these maliciously crafted links can only be reasonably made for known jupyter server hosts. A link to your jupyter server may *appear* safe, but ultimately redirect to a spoofed server on the public internet. This same vulnerability was patched in upstream notebook v5.7.8. ### Patches _Has the problem been patched? What versions should users upgrade to?_ Patched in jupyter_server 1.1.1. If upgrade is not available, a workaround can be to run your server on a url prefix: ``` jupyter server --ServerApp.base_url=/jupyter/ ``` ### References [OWASP page on open redirects](https://cheatsheetseries.owasp.org/cheatsheets/Unvalidated_Redirects_and_Forwards_Cheat_Sheet.html) ### For more information If you have any questions or comments about this advisory, or vulnerabilities to report, please email our security list [security@ipython.org](mailto:security@ipython.org). Credit: Yaniv Nizry from CxSCA group at Checkmarx

CVE-2020-26275 Affected Jupyter server Versions

1 component(s)
Fixed Versions:
1.1.1
Product / Package Ecosystem Affected Versions Fixed Version
jupyter-server
pypi/jupyter-server
PyPI
< 1.1.1
1.1.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-9f66-54xg-pc2c
NVD — CVE-2020-26275 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-26275
Security Fix Commit FIX COMMIT
https://github.com/jupyter-server/jupyter_server/commit/85e4abccf6ea9321d29153f73b0bd72ccb3a6bca
advisory.checkmarx.net/advisory/cx-2020-42... WEB
https://advisory.checkmarx.net/advisory/CX-2020-4291
Jupyter server Source Repository REPOSITORY
https://github.com/jupyter-server/jupyter_server
Jupyter server Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/jupyter-server/PYSEC-2020-346.yaml
Jupyter server Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/jupyter-server/PYSEC-2020-50.yaml
pypi.org/project/jupyter-ser... WEB
https://pypi.org/project/jupyter-server

Frequently Asked Questions

What is CVE-2020-26275?
CVE-2020-26275 is a security vulnerability in Jupyter server involving Jupyter Server open redirect vulnerability under CWE-601: URL Redirection to Untrusted Site ('Open Redirect').
Which Jupyter server versions are affected?
Affected versions include releases prior to 1.1.1 across affected packages: jupyter-server.
What version fixes CVE-2020-26275?
Upgrading to 1.1.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is jupyter-server affected?
Yes, jupyter-server is affected in releases prior to 1.1.1. Upgrade your dependency to 1.1.1 or later.
What is the CVSS score of CVE-2020-26275?
CVE-2020-26275 has a CVSS v3.1 base score of 6.1 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2020-26275?
CVE-2020-26275 is classified under CWE-601: URL Redirection to Untrusted Site ('Open Redirect') (The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.).
How can I check PyPI dependencies for CVE-2020-26275?
Run the dependency tree command: 'pip show jupyter-server'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9f66-54xg-pc2c",
  "modified" : "2026-05-19T20:24:16Z",
  "published" : "2020-12-21T18:01:41Z",
  "aliases" : [ "CVE-2020-26275" ],
  "summary" : "Jupyter Server open redirect vulnerability",
  "details" : "### Impact\n_What kind of vulnerability is it? Who is impacted?_\n\nOpen redirect vulnerability - a maliciously crafted link to a jupyter server could redirect the browser to a different website.\n\nAll jupyter servers running without a base_url prefix are technically affected, however, these maliciously crafted links can only be reasonably made for known jupyter server hosts. A link to your jupyter server may *appear* safe, but ultimately redirect to a spoofed server on the public internet. This same vulnerability was patched in upstream notebook v5.7.8.\n\n### Patches\n\n_Has the problem been patched? What versions should users upgrade to?_\n\nPatched in jupyter_server 1.1.1. If upgrade is not available, a workaround can be to run your server on a url prefix:\n\n```\njupyter server --ServerApp.base_url=/jupyter/\n```\n\n### References\n\n[OWASP page on open redirects](https://cheatsheetseries.owasp.org/cheatsheets/Unvalidated_Redirects_and_Forwards_Cheat_Sheet.html)\n\n### For more information\n\nIf you have any questions or comments about this advisory, or vulnerabilities to report, please email our security list [security@ipython.org](mailto:security@ipython.org).\n\nCredit: Yaniv Nizry from CxSCA group at Checkmarx",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "jupyter-server"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.1.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-9f66-54xg-pc2c"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-26275"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/jupyter-server/jupyter_server/commit/85e4abccf6ea9321d29153f73b0bd72ccb3a6bca"
  }, {
    "type" : "WEB",
    "url" : "https://advisory.checkmarx.net/advisory/CX-2020-4291"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/jupyter-server/jupyter_server"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/jupyter-server/PYSEC-2020-346.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/jupyter-server/PYSEC-2020-50.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://pypi.org/project/jupyter-server"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-601" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2020-12-21T18:00:51Z",
    "nvd_published_at" : "2020-12-21T18:15:00Z"
  }
}