CVE-2026-31838
MEDIUMCVSS Vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
2Description
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.
Analysis
Istio versions prior to 1.29.1, 1.28.5, and 1.27.8 are vulnerable to authorization policy bypass through improper Envoy RBAC handling of multi-valued HTTP headers. An attacker can craft requests with multiple header values that cause the authorization engine to evaluate headers differently than intended, allowing unauthorized access to protected microservices. …
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Remediation
Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Monitor vendor channels for patch availability.
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External POC / Exploit Code
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