Improper access control in Istio - CVE-2026-31838
Published: April 20, 2026
Vulnerability identifier: #VU126609
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-31838
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to disclose sensitive information.
The vulnerability exists due to improper access control in Envoy RBAC header matching when handling requests with multiple HTTP header values. A remote attacker can send a specially crafted request with multiple header values to disclose sensitive information.
This may allow unauthorized requests to reach protected services when authorization policies rely on such header-based matching conditions.
Affected software
Istio
How to mitigate CVE-2026-31838
Install security update from vendor's website.
Istio - addressed in versions 1.27.8, 1.28.5, 1.29.1