CVE-2025-61669 jupyter_server next parameter open redirect can redirect users to external domains
Attackers can redirect users to malicious external domains via the login next parameter, facilitating phishing attacks against Jupyter Server users.
- 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-2025-61669?
CVE-2025-61669 is a medium-severity vulnerability in jupyter-server jupyter_server, published on 5 May 2026. 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
Jupyter Server is the backend for Jupyter web applications. In jupyter_server versions through 2.17.0, the next query parameter in the login flow is insufficiently validated in `LoginFormHandler._redirect_safe()`, which allows redirects to arbitrary external domains via values such as `///example.com`. An attacker can use a crafted login URL to redirect users to a malicious site and facilitate phishing attacks. This issue is fixed in version 2.18.0.
Weakness: CWE-601
Which versions are affected by CVE-2025-61669?
3 open source packages ship an affected version, including jupyter-server. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
jupyter-server PyPI | All versions | 2.18.0 |
jupyter-server PyPI | All versions | 2.18.0 |
jupyter-server PyPI | All versions | 2.18.0 |
Products include Jupyter Jupyter Server.
How do I fix CVE-2025-61669?
Upgrade jupyter-server to 2.18.0 or later.
Is CVE-2025-61669 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-61669 exists.
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 CLEANSTART-2026-JD56309, CLEANSTART-2026-ZJ86247, DEBIAN-CVE-2025-61669, GHSA-qh7q-6qm3-653w, PYSEC-2026-67, UBUNTU-CVE-2025-61669.