---
id: "CVE-2026-97032"
kind: "vulnerability"
aliases: ["CVE-2026-97032", "GO-2026-6617"]
title: "HTTP/2 server crash due to HPACK encoder race in net/http"
severity: "high"
cvss: 7.5
epss: 0.0042
exploited: false
status: "open"
category: "runtime"
products: [{"name": "stdlib", "fixed": ["1.26.9"], "affected": "< 1.26.9", "ecosystem": "go"}, {"name": "stdlib", "fixed": ["1.27.2"], "affected": ">= 1.27.0-0, < 1.27.2", "ecosystem": "go"}, {"name": "golang.org/x/net", "fixed": ["0.60.0"], "affected": "< 0.60.0", "ecosystem": "go"}]
ecosystems: ["go"]
tags: ["go", "golang.org/x/net", "http2", "net/http", "runtime", "self-hosted"]
not_affected_if: ["http1-only", "managed-hosting"]
published_at: "2026-10-08T22:31:09+00:00"
first_seen_at: "2026-10-23T19:13:08+00:00"
updated_at: "2026-10-23T19:56:06+00:00"
sources: [{"source": "govuln", "url": "https://pkg.go.dev/vuln/GO-2026-6617", "first_seen_at": "2026-10-23T19:13:08+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-97032", "first_seen_at": "2026-10-23T19:13:43+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-97032", "first_seen_at": "2026-10-23T19:35:23+00:00"}]
---

# HTTP/2 server crash due to HPACK encoder race in net/http

Go's standard net/http HTTP/2 server can crash because it modifies the HPACK encoder from two goroutines without synchronization when a client changes the header table size. A remote client can repeatedly trigger the race to crash the server, a denial of service.

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

## Affected

- go:stdlib affected < 1.26.9 fixed 1.26.9
- go:stdlib affected >= 1.27.0-0, < 1.27.2 fixed 1.27.2
- go:golang.org/x/net affected < 0.60.0 fixed 0.60.0

## How to check

Run `go version` on the build host and on the server binary's Go toolchain; affected if stdlib is below 1.26.9 or in 1.27.0 to before 1.27.2. For x/net, check go.mod for golang.org/x/net below 0.60.0.

## Fix

Upgrade the Go toolchain to 1.26.9 or 1.27.2 and rebuild; for golang.org/x/net, update to 0.60.0 or later and rebuild.

## Timeline

- 2026-10-23T19:13:08+00:00 govuln https://pkg.go.dev/vuln/GO-2026-6617
- 2026-10-23T19:13:43+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2026-97032
- 2026-10-23T19:35:23+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-97032

## From the sources

HTTP/2 servers could end up crashing due to inadvertently modifying its HPACK encoder concurrently. This happens because the server modifies the HPACK encoder from two goroutines without synchronization: one uses the encoder to encode a HEADERS frame as part of a response sent to a client and the other modifies the encoder's table size when handling a SETTINGS frame containing SETTINGS_HEADER_TABLE_SIZE that a client sends. A malicious client can repeatedly send a request while changing the header table size to crash the server.

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