Bug 2538810 (CVE-2026-86049)

Summary:	CVE-2026-86049 jupyter-server: Jupyter Server: Information disclosure via 5xx request logging
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	rjohnson
Target Milestone:	---	Keywords:	Security
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Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in Jupyter Server. The server's logging mechanism for HTTP 500 errors fails to properly redact sensitive information. When a request results in an HTTP 500 error and includes a Referer header containing a security token, this token is written to server logs in plaintext. An attacker with access to these logs could retrieve the token, potentially gaining unauthorized access to the affected user's Jupyter Server permissions.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
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Description OSIDB Bzimport 2026-09-22 20:44:32 UTC

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.