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PatchSiren cyber security CVE debrief

CVE-2025-61669 Jupyter CVE debrief

CVE-2025-61669 is a medium-severity open redirect issue in Jupyter Server’s login flow. In affected versions through 2.17.0, an attacker can craft a login URL that redirects a user to an external site after authentication, which can be used for phishing and trust abuse. The issue is fixed in Jupyter Server 2.18.0.

Vendor
Jupyter
Product
Jupyter Server
CVSS
MEDIUM 6.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-05
Original CVE updated
2026-05-11
Advisory published
2026-05-05
Advisory updated
2026-05-11

Who should care

Administrators, security teams, and users of Jupyter Server instances through 2.17.0 should care, especially where login links are shared directly or users may trust post-login redirects. The risk is higher when Jupyter Server is exposed to broad user populations or reachable from the public internet.

Technical summary

The vulnerability is caused by insufficient validation in `LoginFormHandler._redirect_safe()` for the `next` query parameter in the login flow. Crafted values such as `///example.com` can bypass the intended safety check and redirect users to arbitrary external domains. The supplied NVD record maps the issue to CWE-601 and lists affected Jupyter Server versions as all versions through 2.17.0, with 2.18.0 excluded as fixed.

Defensive priority

Medium. Prioritize upgrading because the issue is network-reachable and only requires user interaction, but the primary impact is redirect-based phishing rather than direct server compromise.

Recommended defensive actions

  • Upgrade Jupyter Server to 2.18.0 or later.
  • Review any login links or workflows that pass a `next` parameter and ensure users are not relying on untrusted redirect destinations.
  • If immediate upgrading is not possible, reduce exposure of the login endpoint where practical and warn users to verify destinations after authentication.
  • Track the vendor advisory for any additional remediation guidance or follow-up updates.

Evidence notes

The analysis is based on the official NVD record and the linked GitHub Security Advisory. NVD lists the vulnerable CPE as `jupyter:jupyter_server:*` with an upper bound excluded at 2.18.0, and reports CVSS v4.0 vector `AV:N/AC:L/AT:N/PR:N/UI:P/...`. The GitHub advisory reference identifies the issue as an open redirect in the login flow and ties the fix to version 2.18.0.

Sources and references

Verified primary and authoritative sources

  • CVE-2025-61669 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2025-61669

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2025-61669 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2025-61669

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.