---
title: "CVE-2026-86049: Jupyter Server - Information Disclosure"
description: "Jupyter Server < 2.21.0 contains an information disclosure vulnerability caused by improper token scrubbing of the Referer header in 5xx request logging, letting attackers with log access recover tokens, exploit requires log access."
url: https://panop.io/threat-heartbeat/CVE-2026-86049/
---

# CVE-2026-86049 Jupyter Server - Information Disclosure

Jupyter Server < 2.21.0 contains an information disclosure vulnerability caused by improper token scrubbing of the Referer header in 5xx request logging, letting attackers with log access recover tokens, exploit requires log access.

CVSS base score 7.1 /10

High

CISA KEV

Not listed

Public exploit

None known

EPSS

0.42% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-86049)

## Details

Type

Information Disclosure

Impact

Information Disclosure

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H

Published

17 September 2026

Updated

15 October 2026

Weakness

[CWE-532](https://cwe.mitre.org/data/definitions/532.html)

## Vendor fix

Update to version 2.21.0 or later.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-86049](https://nvd.nist.gov/vuln/detail/CVE-2026-86049)
- [https://github.com/jupyter-server/jupyter\_server/commit/52513529af7096e622c00911b17627b266294717](https://github.com/jupyter-server/jupyter_server/commit/52513529af7096e622c00911b17627b266294717)
- [https://github.com/jupyter-server/jupyter\_server/pull/1681](https://github.com/jupyter-server/jupyter_server/pull/1681)
- [https://github.com/jupyter-server/jupyter\_server/releases/tag/v2.21.0](https://github.com/jupyter-server/jupyter_server/releases/tag/v2.21.0)
- [https://github.com/jupyter-server/jupyter\_server/security/advisories/GHSA-c3mw-737p-c7g2](https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-c3mw-737p-c7g2)

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## What this record can't tell you

- Whether you run the affected software, and where
- Whether an attacker can actually reach and exploit it
- The misconfigurations that never get a CVE number
- What it would cost the business, ranked into what to fix first

Panop answers these inside your environment, for this CVE and every other finding.

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