Bug 2540685 (CVE-2026-96748)

Summary:	CVE-2026-96748 pymongo: pymongo: Database connection redirection via percent-encoded host delimiter injection
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:	eglynn, jjoyce, jpretori, jschluet, lhh, mburns, mgarciac
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in pymongo. The driver improperly decodes percent-encoded characters in connection strings before separating host entries on delimiters. If an application incorporates untrusted hostnames into its connection strings, a remote attacker can inject arbitrary servers into the database client configuration. As a result, the application may connect to an attacker-controlled server, leading to data tampering and information disclosure.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
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Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2542960, 2542961
Bug Blocks:

Description OSIDB Bzimport 2026-09-24 18:33:10 UTC

PyMongo's connection string parsing decodes percent-encoded characters in the host portion before the host list is separated on its delimiters. When an application places a hostname value supplied by an unauthenticated party into a connection string, that party may cause additional servers of their choosing to be added to the application's database client. The application may then send its authentication exchange and database operations to one of those servers, which can observe limited information and return altered results.