Jupyter Server open redirect vulnerability

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

5.3 · 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 · score source

EPSS

• CVE-2020-26275: 1.37% estimated exploitation activity in the next 30 days; percentile 72.00 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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 baseurl 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 jupyterserver 1.1.1. If upgrade is not available, a workaround can be to run your server on a url prefix: References OWASP page on open redirects 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. Credit: Yaniv Nizry from CxSCA group at Checkmarx

Published by the source

21 Dec 2020, 18:01 UTC

Last modified by the source

9 Jul 2026, 16:56 UTC

Source last checked

26 Oct 2026, 13:41 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-9f66-54xg-pc2c

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-9f66-54xg-pc2c

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# Patch Next advisory brief: CVE-2020-26275

Advisory: Jupyter Server open redirect vulnerability
IDs: CVE-2020-26275, GHSA-9f66-54xg-pc2c
Record: https://patchnext.com/advisories/cve-2020-26275 (revision 3, source checked 26 Oct 2026, 13:41 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: jupyter-server 1.1.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI jupyter-server: affected < 1.1.1; fixed in 1.1.1

## Suggested inspection (read-only)
- `python -m pip show jupyter-server`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on jupyter-server.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-9f66-54xg-pc2c (OSV record GHSA-9f66-54xg-pc2c lists affected ranges: PyPI jupyter-server >=0 <1.1.1 (fixed))
- Verified: https://github.com/advisories/GHSA-9f66-54xg-pc2c (GitHub-reviewed advisory GHSA-9f66-54xg-pc2c lists affected ranges: PyPI jupyter-server >=0 <1.1.1)

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