CVE-2021-39156: Istio

High severity, CVSS 7.5. EPSS: 1.2% chance of exploitation in the next 30 days.

Istio is an open source platform for providing a uniform way to integrate microservices, manage traffic flow across microservices, enforce policies and aggregate telemetry data. Istio 1.11.0, 1.10.3 and below, and 1.9.7 and below contain a remotely exploitable vulnerability where an HTTP request with `#fragment` in the path may bypass Istio’s URI path based authorization policies. Patches are available in Istio 1.11.1, Istio 1.10.4 and Istio 1.9.8. As a work around a Lua filter may be written to normalize the path.

Affected products

• Istio Istio: before 1.9.8 (fixed in 1.9.8); from 1.10.0, before 1.10.3 (fixed in 1.10.3); from 1.11.0, before 1.11.1 (fixed in 1.11.1)

Published 2021-08-24. Last modified 2026-06-17.