Bug 2562188 (CVE-2026-116672)

Summary:	CVE-2026-116672 authlib: authlib: Authorization bypass via missing client token verification
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	anpicker, anthomas, dfreiber, dkeler, doconnor, drow, dschmidt, ebourniv, ehelms, ggainey, hasun, ilpinto, jburrell, jfula, jlanda, jowilson, jpasqual, juwatts, kshier, ltomasbo, mdellweg, mhayden, mhulan, nmoumoul, nyancey, ometelka, osousa, pcreech, ptisnovs, rbobbitt, rchan, rjohnson, sbunciak, sdoran, simaishi, smallamp, stcannon, suppawar, syedriko, thason, tmalecek, vkumar, xdharmai, yguenane, ykashtan
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in Authlib. An authenticated remote attacker can bypass authorization controls to access, modify, or delete configurations belonging to other clients. In deployments implementing the documented reference code for dynamic client configuration, the server validates client editability without confirming that the presented registration access token belongs to the target client. Consequently, an attacker possessing any valid registration token can alter client settings to intercept authorization tokens or delete registrations, causing a denial of service.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2562908, 2562909, 2562911, 2562912, 2562913
Bug Blocks:

Description OSIDB Bzimport 2026-10-27 18:15:09 UTC

Authlib is a Python library which builds OAuth and OpenID Connect servers. From 0.15 until 1.9.1, the documented ClientConfigurationEndpoint.authenticate_client and ClientConfigurationEndpoint.check_permission reference implementations look up a target client from request-controlled client_id data and check only whether that target is editable, without verifying that request.credential belongs to the target client. Deployments following both examples can allow a client holding any valid registration access token to read, modify, or delete another client's registration. Changing redirect_uris can enable authorization code or token interception, while deleting registrations can deny service to affected clients. This issue is fixed in version 1.9.1.