CVE-2020-26275 Open redirect vulnerability
Attackers can craft links that appear safe but redirect users to malicious sites, affecting Jupyter Server instances without a base URL prefix.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2020-26275?
CVE-2020-26275 is a medium-severity vulnerability in jupyter-server jupyter_server, published on 21 Dec 2020. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
The Jupyter Server provides the backend (i.e. the core services, APIs, and REST endpoints) for Jupyter web applications like Jupyter notebook, JupyterLab, and Voila. In Jupyter Server before version 1.1.1, an open redirect vulnerability could cause the jupyter server to redirect the browser to a different malicious 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. This is fixed 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/".
Weakness: CWE-601
Which versions are affected by CVE-2020-26275?
3 open source packages ship an affected version, including jupyter-server. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
jupyter-server PyPI | All versions | 1.1.1 |
jupyter-server PyPI | All versions | 1.1.1 |
jupyter-server PyPI | All versions | 1.1.1 |
Products include Jupyter Jupyter Server.
How do I fix CVE-2020-26275?
Upgrade jupyter-server to 1.1.1 or later.
Is CVE-2020-26275 being exploited?
There is no known exploitation of CVE-2020-26275 in the wild and no public exploit code.
Other vulnerabilities in jupyter-server jupyter_server
- CVE-2026-44727 Jupyter Server: Stored XSS in `NbconvertFileHandler` / `NbconvertPostHandler` via missing `sandbox` CSP
- CVE-2026-35397 jupyter-server path traversal allows access to sibling directories sharing root_dir name prefix
- CVE-2026-40110 jupyter-server CORS origin validation bypass via unanchored regex in allow_origin_pat
- CVE-2026-40934 jupyter-server authentication cookies remain valid after password reset due to static cookie secret
- CVE-2024-35178 Jupyter server on Windows discloses Windows user password hash
Sources
Also known as DEBIAN-CVE-2020-26275, GHSA-9f66-54xg-pc2c, PYSEC-2020-50, UBUNTU-CVE-2020-26275.