Bug 2446342 (CVE-2026-31838)

Summary:	CVE-2026-31838 istio: Istio: Authorization policy bypass via Envoy RBAC header matching with multiple header values
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	alebedev, dhanak, drosa, dschmidt, dsimansk, erezende, jkoehler, jlanda, kingland, kshier, kverlaen, lphiri, mnovotny, sausingh, simaishi, smcdonal, stcannon, teagle, yguenane
Target Milestone:	---	Keywords:	Security
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Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in Istio. This vulnerability in Envoy's Role-Based Access Control (RBAC) header matching could allow an attacker to bypass authorization policies. By crafting requests with multiple header values, an attacker could cause Envoy to misinterpret the header, leading to unauthorized access to protected services.	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 2026-03-10 23:03:15 UTC

Istio is an open platform to connect, manage, and secure microservices. Prior to 1.29.1, 1.28.5, and 1.27.8, a vulnerability in Envoy RBAC header matching could allow authorization policy bypass when policies rely on HTTP headers that may contain multiple values. An attacker could craft requests with multiple header values in a way that causes Envoy to evaluate the header differently than intended, potentially bypassing authorization checks. This may allow unauthorized requests to reach protected services when policies depend on such header-based matching conditions. This vulnerability is fixed in 1.29.1, 1.28.5, and 1.27.8.