Description
Jupyter Server is the backend for Jupyter web applications. Prior to version 2.21.0, the 5xx request logging path in jupyter_server/log.py copies the Referer header into a JSON header block without applying the token scrubbing used for the request URI. A request that returns HTTP 500 while the Referer contains a token-bearing URL can therefore write that token to server logs in plaintext. An attacker who can read those logs can recover the token and use the affected user's Jupyter Server permissions. This issue is fixed in version 2.21.0.
Published: 2026-09-17
Score: 7.1 High
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

No vendor fix or workaround currently provided.

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Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-c3mw-737p-c7g2 Jupyter Server: 5xx request logging leaks token-bearing Referer header values
History

Fri, 18 Sep 2026 21:30:00 +0000

Type Values Removed Values Added
First Time appeared Jupyter
Jupyter jupyter Server
Vendors & Products Jupyter
Jupyter jupyter Server
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}


Thu, 17 Sep 2026 20:45:00 +0000

Type Values Removed Values Added
Description Jupyter Server is the backend for Jupyter web applications. Prior to version 2.21.0, the 5xx request logging path in jupyter_server/log.py copies the Referer header into a JSON header block without applying the token scrubbing used for the request URI. A request that returns HTTP 500 while the Referer contains a token-bearing URL can therefore write that token to server logs in plaintext. An attacker who can read those logs can recover the token and use the affected user's Jupyter Server permissions. This issue is fixed in version 2.21.0.
Title Jupyter Server: 5xx request logging leaks token-bearing Referer header values
Weaknesses CWE-532
References
Metrics cvssV3_1

{'score': 7.1, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H'}


Subscriptions

Jupyter Jupyter Server
cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-09-18T18:32:48.654Z

Reserved: 2026-09-04T19:29:21.058Z

Link: CVE-2026-86049

cve-icon Vulnrichment

Updated: 2026-09-18T17:24:13.674Z

cve-icon NVD

Status : Received

Published: 2026-09-17T21:17:50.213

Modified: 2026-09-18T19:17:08.143

Link: CVE-2026-86049

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-09-18T21:30:14Z

Weaknesses
  • CWE-532

    Insertion of Sensitive Information into Log File