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GHSA-qh7q-6qm3-653w

MediumCVSS 6 / 10
Published May 5, 2026·Last modified May 8, 2026
Affected Components(0)

No affected components available

Description

Summary

The ?next=... URL query parameter has an open redirection vulnerability. In jupyter_server<=2.17.0, this URL query parameter allows redirection to arbitrary external domains, which can be exploited to facilitate phishing attacks on server users.

Details

The vulnerability is caused by insufficient validation in the LoginFormHandler._redirect_safe() method.

  • Source code reference: https://github.com/jupyter-server/jupyter_server/blob/987ebdd5e188cdc49751b01a0d6782d686492a53/jupyter_server/auth/login.py#L33-L76

This vulnerability was originally reported by Noriaki Iwasaki. All discovery credit goes to them.

PoC

  1. Navigate to http://localhost:8888/login?next=///google.com
  2. Observe that the user is redirected to google.com despite it being an external domain.

The external domain passed in the ?next parameter may be replaced with a malicious lookalike to facilitate phishing attacks. Jupyter Server deployments served on a public domain are especially vulnerable, as prod.company.com may be redirected to a look-alike URL such as prod.company.dev.

Impact

This vulnerability affects all users, especially enterprise users who work with sensitive/confidential data.

Patches

Jupyter Server 2.18+

Workaround

None.

Risk Scores
Base Score
6.0

The vulnerability requires local access to the device to be exploited. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights.

Threat Intelligence
2.0

Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.

EPSS
0.27%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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