# CVE-2025-61669: jupyter-server: Jupyter Server is the backend for Jupyter web applications

CVE-2025-61669 is fixed in jupyter-server on 1 platform by DEBIAN-CVE-2025-61669 (version 2.20.0-1), released May 5, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2025-61669
- Priority: Routine
- CVSS: 6.1 (medium)
- EPSS: 0.0024
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 5, 2026

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | jupyter-server Debian 14 | 2.20.0-1 | [DEBIAN-CVE-2025-61669](https://patchblox.com/security/data/fix/linux/debian-cve-2025-61669.md) | May 5, 2026 |

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Data as of 2026-11-08T06:59:42Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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