diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8095780..cc18ec6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -16,7 +16,7 @@ concurrency:
   cancel-in-progress: true
 
 env:
-  GO_VERSION: 1.26.5
+  GO_VERSION: 1.26.6
   NODE_VERSION: 24.19.0
   BUILDX_METADATA_PROVENANCE: "false"
   DOCKER_BUILD_RECORD_UPLOAD: "false"
diff --git a/.github/workflows/security.yml b/.github/workflows/security.yml
index bd4dc60..fc275e9 100644
--- a/.github/workflows/security.yml
+++ b/.github/workflows/security.yml
@@ -19,7 +19,7 @@ concurrency:
   cancel-in-progress: true
 
 env:
-  GO_VERSION: 1.26.5
+  GO_VERSION: 1.26.6
   NODE_VERSION: 24.19.0
 
 jobs:
@@ -109,7 +109,7 @@ jobs:
           package-manager-cache: true
 
       - name: Initialize CodeQL
-        uses: github/codeql-action/init@5595ccaf912efad79be6eef63a5619ff05969be3 # v4
+        uses: github/codeql-action/init@ff2f1c621b7f889edc0d3c761ac2e6a3f8cdb0dd # v4
         with:
           languages: ${{ matrix.language }}
 
@@ -123,4 +123,4 @@ jobs:
         run: go build ./cmd/multispeed
 
       - name: Analyze
-        uses: github/codeql-action/analyze@5595ccaf912efad79be6eef63a5619ff05969be3 # v4
+        uses: github/codeql-action/analyze@ff2f1c621b7f889edc0d3c761ac2e6a3f8cdb0dd # v4
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 86e26cd..e265d0e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,10 @@ All notable changes to MultiSpeed are documented here. The project follows [Sema
 
 ## [Unreleased]
 
+### Security
+
+- Upgrade the build toolchain to Go 1.26.6 and the patched LibreSpeed overlay to `golang.org/x/net` v0.56.0.
+
 ## [1.0.4] - 2026-08-11
 
 ### Fixed
diff --git a/Dockerfile b/Dockerfile
index def61df..6fb6f91 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,7 +1,7 @@
 # syntax=docker/dockerfile:1.7
 
 ARG NODE_VERSION=24.19.0
-ARG GO_VERSION=1.26.5
+ARG GO_VERSION=1.26.6
 ARG DEBIAN_RELEASE=bookworm
 
 FROM node:${NODE_VERSION}-${DEBIAN_RELEASE}-slim@sha256:3638d9a6fe4030bd716be989438248074489337ba3275657f93595428be4fc03 AS frontend-build
@@ -21,10 +21,10 @@ RUN npm run build && \
       /out/dependency-licenses \
       /license-overrides/npm
 
-FROM golang:${GO_VERSION}-${DEBIAN_RELEASE}@sha256:8d36439c36258ba98de1bf2b316eda72905f9d743117119f6db9705c49245644 AS librespeed-build
+FROM golang:${GO_VERSION}-${DEBIAN_RELEASE}@sha256:116d58cbd88c1297624acc6e967a060012422bacf9930927e23fb719189c6f36 AS librespeed-build
 ARG LIBRESPEED_VERSION=v1.0.13
-ARG LIBRESPEED_PATCH_VERSION=multispeed.dns2.xnet055
-ARG LIBRESPEED_X_NET_VERSION=v0.55.0
+ARG LIBRESPEED_PATCH_VERSION=multispeed.dns2.xnet056
+ARG LIBRESPEED_X_NET_VERSION=v0.56.0
 ARG BUILD_DATE=unknown
 ENV CGO_ENABLED=0 \
     GOOS=linux \
@@ -78,7 +78,7 @@ RUN --mount=type=cache,target=/go/pkg/mod \
     cd /out/source; \
     sha256sum "librespeed-cli-${LIBRESPEED_VERSION}-multispeed-corresponding-source.tar.gz" > "librespeed-cli-${LIBRESPEED_VERSION}-multispeed-corresponding-source.tar.gz.sha256"
 
-FROM golang:${GO_VERSION}-${DEBIAN_RELEASE}@sha256:8d36439c36258ba98de1bf2b316eda72905f9d743117119f6db9705c49245644 AS backend-build
+FROM golang:${GO_VERSION}-${DEBIAN_RELEASE}@sha256:116d58cbd88c1297624acc6e967a060012422bacf9930927e23fb719189c6f36 AS backend-build
 ARG VERSION=dev
 ARG VCS_REF=unknown
 ARG BUILD_DATE=unknown
@@ -113,8 +113,8 @@ ARG VERSION=dev
 ARG VCS_REF=unknown
 ARG BUILD_DATE=unknown
 ARG LIBRESPEED_VERSION=v1.0.13
-ARG LIBRESPEED_PATCH_VERSION=multispeed.dns2.xnet055
-ARG LIBRESPEED_X_NET_VERSION=v0.55.0
+ARG LIBRESPEED_PATCH_VERSION=multispeed.dns2.xnet056
+ARG LIBRESPEED_X_NET_VERSION=v0.56.0
 
 LABEL org.opencontainers.image.title="MultiSpeed" \
       org.opencontainers.image.description="Production-ready multi-WAN speed-test monitor" \
diff --git a/README.md b/README.md
index dd7fa46..361e60f 100644
--- a/README.md
+++ b/README.md
@@ -190,7 +190,7 @@ No environment-variable values are exposed by the system API.
 
 ## Development
 
-Prerequisites are Go 1.26.5, Node.js 24, npm 11, and Linux for networking/integration behavior.
+Prerequisites are Go 1.26.6, Node.js 24, npm 11, and Linux for networking/integration behavior.
 
 ```bash
 go mod download
diff --git a/THIRD_PARTY_NOTICES.md b/THIRD_PARTY_NOTICES.md
index 3b64e31..b54a69b 100644
--- a/THIRD_PARTY_NOTICES.md
+++ b/THIRD_PARTY_NOTICES.md
@@ -12,9 +12,9 @@ MultiSpeed is MIT-licensed. Third-party components remain under their respective
 - License: GNU Lesser General Public License v3.0 (LGPL-3.0-only)
 - Relationship: separately built and separately executed, replaceable subprocess; it is not linked into the MultiSpeed binary
 
-The production image builds LibreSpeed CLI from the tagged source and applies the MultiSpeed `multispeed.dns2.xnet055` overlay under LGPL-3.0-or-later. The overlay makes UDP DNS and TCP fallback bind the same selected source address as the HTTP test sockets, pins authorized custom runs to their pre-resolved IP:port endpoints, blocks redirects before follow-up requests, and pins `golang.org/x/net` v0.55.0 in place of upstream v0.49.0. The image and release assets include a deterministic complete corresponding-source archive containing the exact patched tree, vendored dependency source, build script, integration test, module metadata, and the full GPLv3 and LGPLv3 license texts. Telemetry is disabled by default.
+The production image builds LibreSpeed CLI from the tagged source and applies the MultiSpeed `multispeed.dns2.xnet056` overlay under LGPL-3.0-or-later. The overlay makes UDP DNS and TCP fallback bind the same selected source address as the HTTP test sockets, pins authorized custom runs to their pre-resolved IP:port endpoints, blocks redirects before follow-up requests, and pins `golang.org/x/net` v0.56.0 in place of upstream v0.49.0. The image and release assets include a deterministic complete corresponding-source archive containing the exact patched tree, vendored dependency source, build script, integration test, module metadata, and the full GPLv3 and LGPLv3 license texts. Telemetry is disabled by default.
 
-LibreSpeed CLI copyright remains with its upstream contributors. It is provided without warranty under LGPL-3.0-only; the MultiSpeed overlay files are offered under LGPL-3.0-or-later. You may replace `/usr/local/bin/librespeed-cli` in a private deployment with a compatible build, subject to the component's license. MultiSpeed fails closed unless that build advertises the `+multispeed.dns2.xnet055` marker and therefore attests to the required source-bound resolver, destination-pinning, and patched dependency baseline.
+LibreSpeed CLI copyright remains with its upstream contributors. It is provided without warranty under LGPL-3.0-only; the MultiSpeed overlay files are offered under LGPL-3.0-or-later. You may replace `/usr/local/bin/librespeed-cli` in a private deployment with a compatible build, subject to the component's license. MultiSpeed fails closed unless that build advertises the `+multispeed.dns2.xnet056` marker and therefore attests to the required source-bound resolver, destination-pinning, and patched dependency baseline.
 
 ## Optional operator component not distributed by MultiSpeed
 
diff --git a/docs/development.md b/docs/development.md
index 8587950..ec5e638 100644
--- a/docs/development.md
+++ b/docs/development.md
@@ -4,7 +4,7 @@ MultiSpeed's networking behavior is Linux-specific. Editing and unit tests can r
 
 ## Toolchain
 
-- Go 1.26.5
+- Go 1.26.6
 - Node.js 24 and npm 11
 - Docker Engine with Compose v2 and BuildKit
 - `golangci-lint` v2 (version pinned in CI)
diff --git a/docs/providers.md b/docs/providers.md
index 517edd2..ff2ebea 100644
--- a/docs/providers.md
+++ b/docs/providers.md
@@ -18,7 +18,7 @@ Cloudflare is a trademark and/or registered trademark of Cloudflare, Inc. MultiS
 
 The production image builds official `librespeed/speedtest-cli` v1.0.13 from the immutable source tag as a separate, replaceable executable, then applies MultiSpeed's small LGPL source-bound DNS and destination-pinning overlay. Runtime notices, the complete overlay, license texts, and dependency notices are shipped under `/usr/share/doc/librespeed-cli`; the deterministic complete corresponding-source archive and checksum are under `/opt/multispeed/release-artifacts` and attached to each GitHub release.
 
-MultiSpeed uses JSON output, `--source <address>`, `--no-icmp`, a bounded timeout, and `--telemetry-level disabled`. Upstream v1.0.13 binds HTTP sockets for `--source` but otherwise leaves DNS on the default resolver; the overlay installs a pure-Go resolver whose UDP and TCP connections bind the same source address, pins authorized custom runs to the pre-resolved IP addresses and canonical port, and rejects redirects before a follow-up request. The build replaces upstream's vulnerable `golang.org/x/net` v0.49.0 with pinned v0.55.0. The adapter refuses a replacement CLI unless its version carries the `+multispeed.dns2.xnet055` compatibility marker, preventing an unpatched or dependency-vulnerable executable from silently weakening the release baseline. It supports automatic selection, a public server ID, and deployment-authorized custom server definitions. Certificate verification remains enabled by default; any per-server bypass must be explicit and is recorded in result metadata.
+MultiSpeed uses JSON output, `--source <address>`, `--no-icmp`, a bounded timeout, and `--telemetry-level disabled`. Upstream v1.0.13 binds HTTP sockets for `--source` but otherwise leaves DNS on the default resolver; the overlay installs a pure-Go resolver whose UDP and TCP connections bind the same source address, pins authorized custom runs to the pre-resolved IP addresses and canonical port, and rejects redirects before a follow-up request. The build replaces upstream's vulnerable `golang.org/x/net` v0.49.0 with pinned v0.56.0. The adapter refuses a replacement CLI unless its version carries the `+multispeed.dns2.xnet056` compatibility marker, preventing an unpatched or dependency-vulnerable executable from silently weakening the release baseline. It supports automatic selection, a public server ID, and deployment-authorized custom server definitions. Certificate verification remains enabled by default; any per-server bypass must be explicit and is recorded in result metadata.
 
 Custom backend URLs are fail-closed. The deployment must list each complete base URL in the comma-separated `APP_ALLOWED_CUSTOM_SERVER_URLS` environment variable; an empty value authorizes none. Entries are canonicalized once, and a task URL is accepted only when its canonical form equals an allowlist entry. Credentials, queries, fragments, IPv6 zones, ambiguous hosts, encoded or traversal-like paths, and unsafe path characters are rejected. HTTPS is the default. Listing an `http://` URL authorizes the destination but does not bypass transport policy: the individual task must also enable its existing `allowInsecure` option. Keep this list limited to LibreSpeed servers operated or explicitly trusted by the deployment owner.
 
diff --git a/internal/execution/manager_test.go b/internal/execution/manager_test.go
index 0d99923..5868f80 100644
--- a/internal/execution/manager_test.go
+++ b/internal/execution/manager_test.go
@@ -42,7 +42,7 @@ type availabilityOnlyLibreSpeedRunner struct {
 func (r *availabilityOnlyLibreSpeedRunner) Run(_ context.Context, request providerprocess.Request) (providerprocess.Result, error) {
 	if len(request.Arguments) == 1 && request.Arguments[0] == "--version" {
 		r.versionCalls.Add(1)
-		return providerprocess.Result{Stdout: "librespeed-cli v1.0.13+multispeed.dns2.xnet055"}, nil
+		return providerprocess.Result{Stdout: "librespeed-cli v1.0.13+multispeed.dns2.xnet056"}, nil
 	}
 	r.executionCalls.Add(1)
 	return providerprocess.Result{}, errors.New("unexpected LibreSpeed test execution")
diff --git a/internal/providers/librespeed/librespeed.go b/internal/providers/librespeed/librespeed.go
index a0f373e..5d72cd8 100644
--- a/internal/providers/librespeed/librespeed.go
+++ b/internal/providers/librespeed/librespeed.go
@@ -29,7 +29,7 @@ type Adapter struct {
 }
 
 const (
-	requiredDNSPatchMarker            = "+multispeed.dns2.xnet055"
+	requiredDNSPatchMarker            = "+multispeed.dns2.xnet056"
 	allowedServerEndpointsEnvironment = "MULTISPEED_PROVIDER_ALLOWED_SERVER_ENDPOINTS"
 )
 
diff --git a/internal/providers/librespeed/librespeed_test.go b/internal/providers/librespeed/librespeed_test.go
index 1efdd59..fd78139 100644
--- a/internal/providers/librespeed/librespeed_test.go
+++ b/internal/providers/librespeed/librespeed_test.go
@@ -20,7 +20,7 @@ func (r *recordingRunner) Run(_ context.Context, request providerprocess.Request
 	if len(request.Arguments) == 1 && request.Arguments[0] == "--version" {
 		version := r.version
 		if version == "" {
-			version = "librespeed-cli v1.0.13+multispeed.dns2.xnet055"
+			version = "librespeed-cli v1.0.13+multispeed.dns2.xnet056"
 		}
 		return providerprocess.Result{Stdout: version}, nil
 	}
@@ -34,7 +34,7 @@ func TestAvailabilityRejectsUnpatchedCLI(t *testing.T) {
 	}
 	for _, version := range []string{
 		"librespeed-cli v1.0.13",
-		"librespeed-cli v1.0.13+multispeed.dns1.xnet055",
+		"librespeed-cli v1.0.13+multispeed.dns2.xnet055",
 	} {
 		adapter := New(binary, &recordingRunner{version: version})
 		availability := adapter.Availability(context.Background())
diff --git a/scripts/docker-smoke.ps1 b/scripts/docker-smoke.ps1
index 78e31cb..8cdc9f0 100644
--- a/scripts/docker-smoke.ps1
+++ b/scripts/docker-smoke.ps1
@@ -83,7 +83,7 @@ try {
     $fixture = @(
         '#!/bin/sh',
         'if [ "${1:-}" = "--version" ]; then',
-        "  printf '%s\n' 'librespeed-cli v1.0.13+multispeed.dns2.xnet055 smoke fixture'",
+        "  printf '%s\n' 'librespeed-cli v1.0.13+multispeed.dns2.xnet056 smoke fixture'",
         '  exit 0',
         'fi',
         'printf ''%s\n'' ''[{"timestamp":"2026-01-01T00:00:00Z","server":{"name":"Local smoke fixture","url":"http://127.0.0.1"},"client":{"ip":"203.0.113.10"},"bytes_sent":62500000,"bytes_received":125000000,"ping":8.25,"jitter":0.75,"upload":50,"download":100,"share":""}]'''
diff --git a/scripts/docker-smoke.sh b/scripts/docker-smoke.sh
index 7192d79..b7c61db 100644
--- a/scripts/docker-smoke.sh
+++ b/scripts/docker-smoke.sh
@@ -25,7 +25,7 @@ mkdir -p "${data_dir}"
 cat >"${fake_cli}" <<'EOF'
 #!/bin/sh
 if [ "${1:-}" = "--version" ]; then
-  printf '%s\n' 'librespeed-cli v1.0.13+multispeed.dns2.xnet055 smoke fixture'
+  printf '%s\n' 'librespeed-cli v1.0.13+multispeed.dns2.xnet056 smoke fixture'
   exit 0
 fi
 printf '%s\n' '[{"timestamp":"2026-01-01T00:00:00Z","server":{"name":"Local smoke fixture","url":"http://127.0.0.1"},"client":{"ip":"203.0.113.10"},"bytes_sent":62500000,"bytes_received":125000000,"ping":8.25,"jitter":0.75,"upload":50,"download":100,"share":""}]'
diff --git a/third_party/librespeed/README.md b/third_party/librespeed/README.md
index 800f932..76be0b8 100644
--- a/third_party/librespeed/README.md
+++ b/third_party/librespeed/README.md
@@ -2,9 +2,9 @@
 
 MultiSpeed builds the immutable `github.com/librespeed/speedtest-cli` v1.0.13
 module, then applies this LGPL-3.0-or-later overlay before compiling it.
-The build also pins `golang.org/x/net` v0.55.0 (and the compatible transitive
-versions selected by Go 1.26.5) instead of upstream's vulnerable v0.49.0.
-The resulting compatibility marker is `+multispeed.dns2.xnet055`.
+The build also pins `golang.org/x/net` v0.56.0 (and the compatible transitive
+versions selected by Go 1.26.6) instead of upstream's vulnerable v0.49.0.
+The resulting compatibility marker is `+multispeed.dns2.xnet056`.
 
 The upstream `--source` implementation sets `net.Dialer.LocalAddr` for HTTP
 connections but leaves hostname lookups on `net.DefaultResolver`. MultiSpeed
diff --git a/third_party/librespeed/build-corresponding-source.sh b/third_party/librespeed/build-corresponding-source.sh
index d32346e..e5a6e53 100644
--- a/third_party/librespeed/build-corresponding-source.sh
+++ b/third_party/librespeed/build-corresponding-source.sh
@@ -8,7 +8,7 @@ export GOOS=linux
 export GOARCH=amd64
 
 version="${LIBRESPEED_VERSION:-v1.0.13}"
-patch_version="${LIBRESPEED_PATCH_VERSION:-multispeed.dns2.xnet055}"
+patch_version="${LIBRESPEED_PATCH_VERSION:-multispeed.dns2.xnet056}"
 build_date="${BUILD_DATE:-unknown}"
 output="${OUTPUT:-./librespeed-cli}"
 
diff --git a/web/e2e/Dockerfile b/web/e2e/Dockerfile
index a4dfa1c..b213e29 100644
--- a/web/e2e/Dockerfile
+++ b/web/e2e/Dockerfile
@@ -1,9 +1,9 @@
 # syntax=docker/dockerfile:1.7
 
-ARG GO_VERSION=1.26.5
+ARG GO_VERSION=1.26.6
 ARG DEBIAN_RELEASE=bookworm
 
-FROM golang:${GO_VERSION}-${DEBIAN_RELEASE}@sha256:8d36439c36258ba98de1bf2b316eda72905f9d743117119f6db9705c49245644 AS build
+FROM golang:${GO_VERSION}-${DEBIAN_RELEASE}@sha256:116d58cbd88c1297624acc6e967a060012422bacf9930927e23fb719189c6f36 AS build
 WORKDIR /src
 COPY go.mod go.sum ./
 RUN --mount=type=cache,target=/go/pkg/mod go mod download
diff --git a/web/e2e/fixtures/librespeed-cli b/web/e2e/fixtures/librespeed-cli
index f7bb39d..0bc879a 100644
--- a/web/e2e/fixtures/librespeed-cli
+++ b/web/e2e/fixtures/librespeed-cli
@@ -3,7 +3,7 @@ set -eu
 
 case " $* " in
   *" --version "*)
-    printf '%s\n' 'librespeed-cli v1.0.13+multispeed.dns2.xnet055 deterministic-e2e'
+    printf '%s\n' 'librespeed-cli v1.0.13+multispeed.dns2.xnet056 deterministic-e2e'
     ;;
   *" --list "*)
     printf '%s\n' '201: Berlin Fixture (https://librespeed.fixture.invalid)  [Sponsor: MultiSpeed E2E @ https://github.com/dude2k/MultiSpeed]'
diff --git a/web/e2e/multispeed.spec.ts b/web/e2e/multispeed.spec.ts
index 88b41d6..5262e56 100644
--- a/web/e2e/multispeed.spec.ts
+++ b/web/e2e/multispeed.spec.ts
@@ -51,7 +51,7 @@ test('complete operator workflow through the real backend and fake provider exec
   expect(providersResponse.ok()).toBe(true)
   const providers = await providersResponse.json() as Array<{ id: string; available: boolean; version: string }>
   expect(providers.find((provider) => provider.id === 'ookla')).toMatchObject({ available: false })
-  expect(providers.find((provider) => provider.id === 'librespeed')).toMatchObject({ available: true, version: 'librespeed-cli v1.0.13+multispeed.dns2.xnet055 deterministic-e2e' })
+  expect(providers.find((provider) => provider.id === 'librespeed')).toMatchObject({ available: true, version: 'librespeed-cli v1.0.13+multispeed.dns2.xnet056 deterministic-e2e' })
 
   await page.goto('/settings')
   await expect(page.getByText('Ookla provider terms & authorization')).toBeVisible()