CVE-2026-31838: Istio HTTP debug endpoints on port 15014 to enforce namespace-based authorization, preventing cross-namespace proxy data access.

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-10 · updated 2026-06-17
Weakness: CWE-863

Description

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.

Affected products

istio: before 1.27.8; from 1.28.0 before 1.28.5; from 1.29.0 before 1.29.1 — fixed in 1.27.8, 1.28.5, 1.29.1

How to fix

Upgrade to a fixed version: istio 1.27.8, 1.28.5, 1.29.1. Check the vendor advisory for mitigations.

References

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