---
id: "CVE-2026-101570"
kind: "vulnerability"
aliases: ["CVE-2026-101570"]
title: "Helidon: HTTP/2 flaw lets unauthenticated network attacker partly crash server"
severity: "low"
cvss: 3.7
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["helidon", "java", "package", "self-hosted"]
not_affected_if: ["default-config", "no-http2-exposure"]
published_at: "2026-10-20T22:18:10+00:00"
first_seen_at: "2026-10-23T21:57:22+00:00"
updated_at: "2026-10-25T04:43:59+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-101570", "first_seen_at": "2026-10-23T21:57:22+00:00"}]
---

# Helidon: HTTP/2 flaw lets unauthenticated network attacker partly crash server

Helidon's HTTP/2 web server component (helidon-webserver-http2) has a flaw that an unauthenticated attacker can reach over the network via HTTP/2. A successful attack causes a partial denial of service, degrading availability without exposing data.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the Helidon version in the project build file (for example the `io.helidon` dependency version in `pom.xml` or `build.gradle`) and see whether it falls in `4.0.0` through `4.5.5`.
- Confirm whether the application uses the `helidon-webserver-http2` artifact.

## Fix

- Move Helidon to a version newer than `4.5.5` as listed in the Oracle advisory; the exact fixed version is unknown from the sources.

## Timeline

- 2026-10-23T21:57:22+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-101570

## From the sources

Vulnerability in the Helidon product of Oracle Fusion Middleware (component: helidon-webserver-http2).  Supported versions that are affected are 4.0.0-4.5.5. Difficult to exploit vulnerability allows unauthenticated attacker with network access via HTTP/2 to compromise Helidon.  Successful attacks of this vulnerability can result in unauthorized ability to cause a partial denial of service (partial DOS) of Helidon. CVSS 3.1 Base Score 3.7 (Availability impacts).  CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L).

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_