cherry-pick 1.26.1 release note (#16543)

Signed-off-by: Daniel Hawton <[email protected]>

Author: dhawton

content/en/news/releases/1.26.x/announcing-1.26.1/index.md

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+---
+title: Announcing Istio 1.26.1
+linktitle: 1.26.1
+subtitle: Patch Release
+description: Istio 1.26.1 patch release notes.
+publishdate: 2025-05-29
+release: 1.26.1
+---
+
+This release contains bug fixes to improve robustness. This release note describes what is different between Istio 1.26.0 and 1.26.1.
+
+## Traffic Management
+
+- **Updated** Gateway API version to `1.3.0` from `1.3.0-rc.1`. ([Issue #56310](https://github.com/istio/istio/issues/56310))
+
+- **Fixed** a regression in Istio 1.26.0 that caused a panic in istiod when processing Gateway API hostnames. ([Issue #56300](https://github.com/istio/istio/issues/56300))
+
+## Security
+
+- **Fixed** an issue in the `pluginca` feature where `istiod` would silently fallback to the self-signed CA if the provided `cacerts` bundle was incomplete. The system now properly validates the presence of all required CA files and fails with an error if the bundle is incomplete.
+
+## Installation
+
+- **Fixed** a panic in `istioctl manifest translate` when the `IstioOperator` config contains multiple gateways. ([Issue #56223](https://github.com/istio/istio/issues/56223))
+
+## istioctl
+
+- **Fixed** false positives when `istioctl analyze` raised error `IST0134` even when `PILOT_ENABLE_IP_AUTOALLOCATE` was set to `true`. ([Issue #56083](https://github.com/istio/istio/issues/56083))