Bug 2458851 (CVE-2026-39350)

Summary: CVE-2026-39350 Istio: github.com/istio/istio: Istio: Authorization bypass via incorrect interpretation of dots in service account names
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in Istio, an open platform designed to connect, manage, and secure microservices. The serviceAccounts and notServiceAccounts fields within Istio's AuthorizationPolicy incorrectly interpret dots (.) as a regular expression matcher. This vulnerability allows an attacker to craft service account names that can bypass intended authorization rules. As a result, an ALLOW policy may grant access to unauthorized service accounts, or a DENY policy may fail to block malicious variants, potentially leading to unauthorized access or information disclosure.
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Description OSIDB Bzimport 2026-04-15 23:01:13 UTC 
Istio is an open platform to connect, manage, and secure microservices. In versions 1.25.0 through 1.27.8, 1.28.0 through 1.28.5, 1.29.0, and 1.29.1, the serviceAccounts and notServiceAccounts fields in AuthorizationPolicy incorrectly interpret dots (.) as a regular expression matcher. Because . is a valid character in a service account name, an AuthorizationPolicy ALLOW rule targeting a service account such as cert-manager.io also matches cert-manager-io, cert-managerXio, etc. A DENY rule targeting the same name fails to block those variants. Fixes are available in versions 1.29.2, 1.28.6, and 1.27.9.
Comment 2 Marco Benatto 2026-04-16 21:03:10 UTC 
Public Upstream commit fixing this issue:
https://github.com/istio/istio/pull/59700/commits/c0be0eadcb50735260082b1ae1973e590474ffa8