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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.

PUBLISHED Reserved 2026-03-09 | Published 2026-03-10 | Updated 2026-03-11 | Assigner GitHub_M




MEDIUM: 6.9CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N

Problem types

CWE-863: Incorrect Authorization

Product status

>= 1.29.0-alpha.0, < 1.29.1
affected

>= 1.28.0-alpha.0, < 1.28.5
affected

< 1.27.8
affected

References

github.com/.../istio/security/advisories/GHSA-974c-2wxh-g4ww

cve.org (CVE-2026-31838)

nvd.nist.gov (CVE-2026-31838)

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