CVE-2026-86049

Jupyter Server: 5xx request logging leaks token-bearing Referer header values

Published: Sep 17, 2026Updated: Sep 18, 2026 Sources: CVE List NVDCWE-532

7.1HIGH

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.

No summary for this CVE yet.

CVSS Vector Breakdown

Exploitability

AV:NAttack Vector

Network

AC:HAttack Complexity

High

PR:LPrivileges Required

Low

UI:RUser Interaction

Required

Scope

S:UScope

Unchanged

Impact

C:HConfidentiality

High

I:HIntegrity

High

A:HAvailability

High

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Weaknesses

CWE-532

Affected Products

jupyter-server

oss-project·USaka jupyter_server, jupyter-scheduler

jupyter_serverOn-prem

AI / ML / notebook-mlops

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

1 technique

Credential Access

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References

https://github.com/jupyter-server/jupyter_server/security/advisories/GHSA-c3mw-737p-c7g2

github.com

https://github.com/jupyter-server/jupyter_server/pull/1681

github.com

https://github.com/jupyter-server/jupyter_server/commit/52513529af7096e622c00911b17627b266294717

github.com

and 1 more references View all →

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