What is CVE-2025-61669?

CVE-2025-61669 is a medium-severity vulnerability in Jupyter Server, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 6.1/10. Published 2026-05-05.

How severe is CVE-2025-61669?

Medium severity. CVSS v3 base score is 6.1 out of 10.

Open Redirect in Jupyter Server

CVE-2025-61669

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.

Vulnerability class: Open Redirect

Published 2026-05-05 · last modified 2026-10-07.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.002 (14.6th percentile), scored 2026-10-20.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 15th percentile — 14.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.002 · change: -0.000

Affected products

Jupyter Server
Jupyter-Server Jupyter Server — versions <= 2.17.0

Weakness classification (CWE)

CWE-601 — URL Redirection to Untrusted Site (Open Redirect)

References

github.com/jupyter-server/jupyter_server/security/advisories/GHSA-qh7q-6qm3-653w (Exploit, Vendor Advisory)

Frequently asked questions

What is CVE-2025-61669?: CVE-2025-61669 is a medium-severity vulnerability in Jupyter Server, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 6.1/10. Published 2026-05-05.
How severe is CVE-2025-61669?: Medium severity. CVSS v3 base score is 6.1 out of 10.