diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index 4fdc0d8..99e5508 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -32,6 +32,7 @@ updates:
   - package-ecosystem: "docker"
     directory: "/"
     schedule:
-      interval: "monthly"
+      interval: "weekly"
+      day: "monday"
     cooldown:
       default-days: 7
diff --git a/.github/workflows/govulncheck.yml b/.github/workflows/govulncheck.yml
new file mode 100644
index 0000000..ef310e4
--- /dev/null
+++ b/.github/workflows/govulncheck.yml
@@ -0,0 +1,30 @@
+name: govulncheck
+
+permissions: {}
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+  schedule:
+    - cron: '0 6 * * 1'
+
+jobs:
+  govulncheck:
+    permissions:
+      contents: read
+    name: Run on Ubuntu
+    runs-on: ubuntu-latest
+    steps:
+      - name: Clone the code
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+        with:
+          persist-credentials: false
+
+      - name: Setup Go
+        uses: actions/setup-go@4a3601121dd01d1626a1e23e37211e3254c1c06c # v6.4.0
+        with:
+          go-version-file: go.mod
+
+      - name: Run govulncheck
+        run: make govulncheck
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index e84cb7b..c769502 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -14,12 +14,16 @@ concurrency:
 jobs:
   release:
     permissions:
-      contents: write
+      contents: write          # gh release create
+      id-token: write          # keyless cosign + actions/attest OIDC (Fulcio/Rekor)
+      attestations: write      # actions/attest — persist attestations
+      artifact-metadata: write # actions/attest — create the artifact storage record
     name: Build and publish release
     runs-on: ubuntu-latest
     environment: release
     env:
       TAG: ${{ github.ref_name }}
+      IMG_REPO: quay.io/cloudscalech/cluster-api-cloudscale-controller
       IMG: quay.io/cloudscalech/cluster-api-cloudscale-controller:${{ github.ref_name }}
     steps:
       - name: Checkout
@@ -34,6 +38,11 @@ jobs:
           go-version-file: go.mod
           cache: false
 
+      # Gate the release on reachable vulnerabilities (incl. stdlib/toolchain)
+      # before we build or push anything.
+      - name: Run govulncheck
+        run: make govulncheck
+
       - name: Login to quay.io
         uses: docker/login-action@650006c6eb7dba73a995cc03b0b2d7f5ca915bee # v4.2.0
         with:
@@ -45,11 +54,85 @@ jobs:
         uses: docker/setup-buildx-action@d7f5e7f509e45cec5c76c4d5afdd7de93d0b3df5 # v4.1.0
 
       - name: Build and push multi-arch image
-        run: make docker-buildx IMG=$IMG PLATFORMS=linux/amd64,linux/arm64
+        id: build
+        uses: docker/build-push-action@53b7df96c91f9c12dcc8a07bcb9ccacbed38856a # v7.3.0
+        with:
+          context: .
+          platforms: linux/amd64,linux/arm64
+          push: true
+          tags: ${{ env.IMG }}
+          build-args: |
+            VERSION=${{ env.TAG }}
+          # We attach our own SLSA provenance + SBOM attestations below with
+          # actions/attest; disable BuildKit's inline provenance so the image
+          # index stays clean and single-sourced.
+          provenance: false
+
+      - name: Install cosign
+        uses: sigstore/cosign-installer@6f9f17788090df1f26f669e9d70d6ae9567deba6 # v4.1.2
+
+      # Keyless signature (Sigstore/OIDC) — verifiable with `cosign verify`.
+      - name: Sign the container image
+        env:
+          DIGEST: ${{ steps.build.outputs.digest }}
+        run: cosign sign --yes "${IMG_REPO}@${DIGEST}"
+
+      # SLSA build provenance attestation, pushed to quay and the GitHub
+      # attestation store (verifiable with `gh attestation verify`).
+      - name: Attest build provenance
+        uses: actions/attest@a1948c3f048ba23858d222213b7c278aabede763 # v4.1.1
+        with:
+          subject-name: ${{ env.IMG_REPO }}
+          subject-digest: ${{ steps.build.outputs.digest }}
+          push-to-registry: true
+
+      - name: Generate SBOM
+        uses: anchore/sbom-action@e22c389904149dbc22b58101806040fa8d37a610 # v0.24.0
+        with:
+          image: ${{ env.IMG_REPO }}@${{ steps.build.outputs.digest }}
+          format: spdx-json
+          output-file: sbom.spdx.json
+          upload-artifact: false
+          upload-release-assets: false
+
+      # SBOM attestation (the same action switches to SBOM mode when sbom-path
+      # is set), pushed to quay and the GitHub attestation store.
+      - name: Attest SBOM
+        uses: actions/attest@a1948c3f048ba23858d222213b7c278aabede763 # v4.1.1
+        with:
+          subject-name: ${{ env.IMG_REPO }}
+          subject-digest: ${{ steps.build.outputs.digest }}
+          sbom-path: sbom.spdx.json
+          push-to-registry: true
 
       - name: Build release manifests
         run: make release-manifests IMG=$IMG
 
+      # Checksums for the clusterctl artifacts + a keyless signature over them.
+      - name: Generate and sign checksums
+        run: |
+          cd dist
+          sha256sum *.yaml > checksums.txt
+          cosign sign-blob --yes \
+            --bundle checksums.txt.bundle \
+            checksums.txt
+
+      # Verify the signature we just created
+      - name: Verify blob
+        run: |
+          cd dist
+          cosign verify-blob --bundle checksums.txt.bundle \
+            --certificate-identity-regexp '^https://github.com/cloudscale-ch/cluster-api-provider-cloudscale/\.github/workflows/release\.yml@refs/tags/' \
+            --certificate-oidc-issuer https://token.actions.githubusercontent.com \
+            checksums.txt
+
+      # SLSA provenance for the release manifest files (GitHub attestation store;
+      # verifiable with `gh attestation verify <file> --owner cloudscale-ch`).
+      - name: Attest release manifests provenance
+        uses: actions/attest@a1948c3f048ba23858d222213b7c278aabede763 # v4.1.1
+        with:
+          subject-path: 'dist/*.yaml'
+
       - name: Create GitHub Release
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
@@ -62,4 +145,7 @@ jobs:
           gh release create "$TAG" \
             --generate-notes \
             $PRERELEASE_FLAG \
-            dist/*.yaml
+            dist/*.yaml \
+            dist/checksums.txt \
+            dist/checksums.txt.bundle \
+            sbom.spdx.json
diff --git a/Dockerfile b/Dockerfile
index 5c197df..7bbe481 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,5 +1,5 @@
-# Build the manager binary
-FROM golang:1.26.3 AS builder
+# BUILDPLATFORM is a predefined BuildKit arg. For a single-platform `docker build` it resolves to the host and is a no-op.
+FROM --platform=${BUILDPLATFORM} golang:1.26.5 AS builder
 ARG TARGETOS
 ARG TARGETARCH
 ARG VERSION=dev
diff --git a/Makefile b/Makefile
index 32d71e9..060f138 100644
--- a/Makefile
+++ b/Makefile
@@ -80,6 +80,10 @@ lint-fix: golangci-lint ## Run golangci-lint linter and perform fixes
 lint-config: golangci-lint ## Verify golangci-lint linter configuration
 	"$(GOLANGCI_LINT)" config verify
 
+.PHONY: govulncheck
+govulncheck: govulncheck-tool ## Run govulncheck to scan for known, reachable vulnerabilities (incl. stdlib/toolchain).
+	"$(GOVULNCHECK)" ./...
+
 ##@ Dependencies
 
 ## Location to install dependencies to
@@ -87,6 +91,9 @@ LOCALBIN := $(shell pwd)/bin
 $(LOCALBIN):
 	mkdir -p "$(LOCALBIN)"
 
+# Host OS/ARCH used to namespace tool binaries in $(LOCALBIN)
+HOST_PLATFORM := $(shell go env GOOS)-$(shell go env GOARCH)
+
 ## Tool Binaries
 KUBECTL ?= kubectl
 KIND ?= kind
@@ -95,6 +102,7 @@ CONTROLLER_GEN ?= $(LOCALBIN)/controller-gen
 ENVTEST ?= $(LOCALBIN)/setup-envtest
 GOLANGCI_LINT = $(LOCALBIN)/golangci-lint
 GINKGO ?= $(LOCALBIN)/ginkgo
+GOVULNCHECK ?= $(LOCALBIN)/govulncheck
 
 ##@ E2E Testing
 
@@ -378,6 +386,7 @@ ENVTEST_K8S_VERSION ?= $(shell v='$(call gomodver,k8s.io/api)'; \
   printf '%s\n' "$$v" | sed -E 's/^v?[0-9]+\.([0-9]+).*/1.\1/')
 
 GOLANGCI_LINT_VERSION ?= v2.12.2
+GOVULNCHECK_VERSION ?= v1.5.0
 .PHONY: kustomize
 kustomize: $(KUSTOMIZE) ## Download kustomize locally if necessary.
 $(KUSTOMIZE): $(LOCALBIN)
@@ -411,20 +420,25 @@ $(GOLANGCI_LINT): $(LOCALBIN)
 		mv -f $(LOCALBIN)/golangci-lint-custom $(GOLANGCI_LINT); \
 	} || true
 
+.PHONY: govulncheck-tool
+govulncheck-tool: $(GOVULNCHECK) ## Download govulncheck locally if necessary.
+$(GOVULNCHECK): $(LOCALBIN)
+	$(call go-install-tool,$(GOVULNCHECK),golang.org/x/vuln/cmd/govulncheck,$(GOVULNCHECK_VERSION))
+
 # go-install-tool will 'go install' any package with custom target and name of binary, if it doesn't exist
 # $1 - target path with name of binary
 # $2 - package url which can be installed
 # $3 - specific version of package
 define go-install-tool
-@[ -f "$(1)-$(3)" ] && [ "$$(readlink -- "$(1)" 2>/dev/null)" = "$(1)-$(3)" ] || { \
+@[ -f "$(1)-$(3)-$(HOST_PLATFORM)" ] && [ "$$(readlink -- "$(1)" 2>/dev/null)" = "$(1)-$(3)-$(HOST_PLATFORM)" ] || { \
 set -e; \
 package=$(2)@$(3) ;\
-echo "Downloading $${package}" ;\
+echo "Downloading $${package} ($(HOST_PLATFORM))" ;\
 rm -f "$(1)" ;\
 GOBIN="$(LOCALBIN)" go install $${package} ;\
-mv "$(LOCALBIN)/$$(basename "$(1)")" "$(1)-$(3)" ;\
+mv "$(LOCALBIN)/$$(basename "$(1)")" "$(1)-$(3)-$(HOST_PLATFORM)" ;\
 } ;\
-ln -sf "$$(realpath "$(1)-$(3)")" "$(1)"
+ln -sf "$$(realpath "$(1)-$(3)-$(HOST_PLATFORM)")" "$(1)"
 endef
 
 define gomodver
diff --git a/docs/releasing.md b/docs/releasing.md
index ed62651..8fee895 100644
--- a/docs/releasing.md
+++ b/docs/releasing.md
@@ -32,13 +32,19 @@ When introducing a new API version or breaking changes, add a new release series
 4. **The release workflow runs automatically**
 
    Pushing a tag matching `v*.*.*` triggers `.github/workflows/release.yml`, which:
-    - Builds and pushes a multi-arch Docker image (linux/amd64, linux/arm64) to
+    - Gates the release on `make govulncheck` (fails on known, reachable vulnerabilities)
+    - Builds and pushes a Docker image (linux/amd64) to
       `quay.io/cloudscalech/cluster-api-cloudscale-controller:<tag>`
-    - Generates release manifests via `make release-manifests`
+    - Signs the image with keyless [cosign](https://docs.sigstore.dev/) and attaches
+      SLSA build-provenance and an SPDX SBOM as signed attestations
+    - Generates release manifests via `make release-manifests`, a `checksums.txt`
+      signed with `cosign sign-blob`, and SLSA provenance for the manifest files
     - Creates a GitHub release with auto-generated release notes and the following artifacts:
         - `infrastructure-components.yaml` — all CRDs, RBAC, and controller deployment
         - `metadata.yaml` — clusterctl provider metadata
-        - `cluster-template.yaml` — default workload cluster template
+        - `cluster-template*.yaml` / `cluster-class*.yaml` — workload cluster templates
+        - `checksums.txt`, `checksums.txt.bundle` — manifest checksums + Sigstore bundle (signature + certificate)
+        - `sbom.spdx.json` — SBOM of the controller image
 
 ## Post-Release Verification
 
@@ -47,7 +53,112 @@ After the workflow completes:
 1. **Check the GitHub Actions run** succeeded without errors
 2. **Verify the container image** exists
    on [quay.io](https://quay.io/repository/cloudscalech/cluster-api-cloudscale-controller)
-3. **Verify the GitHub release** has all 3 artifacts attached
+3. **Verify the GitHub release** has all artifacts attached (manifests, checksums with bundle,
+   SBOM, release attestation)
 4. **Test installation** on a fresh management cluster.
 
 See [Testing Releases](testing-releases.md) for detailed testing instructions.
+
+Optionally, the release artifacts can be verified using the section below. This is optional because during release
+the verification is already done.
+
+## Verifying a Release
+
+All release artifacts are signed with keyless [Sigstore](https://www.sigstore.dev/)
+signatures using GitHub Actions OIDC. The signing
+identity is this repository's release workflow at the release tag, i.e.
+`https://github.com/cloudscale-ch/cluster-api-provider-cloudscale/.github/workflows/release.yml@refs/tags/<tag>`
+issued by `https://token.actions.githubusercontent.com`.
+
+Requires [`cosign`](https://docs.sigstore.dev/cosign/system_config/installation/)
+and the [GitHub CLI](https://cli.github.com/) (`gh`).
+
+```bash
+export TAG=v1.0.0
+export IMG=quay.io/cloudscalech/cluster-api-cloudscale-controller:$TAG
+export ID_REGEXP='^https://github.com/cloudscale-ch/cluster-api-provider-cloudscale/\.github/workflows/release\.yml@refs/tags/'
+export ISSUER=https://token.actions.githubusercontent.com
+```
+
+### Container image signature
+
+`cosign sign` pushes the signature into the registry alongside the image itself, not to a separate file. We can verify
+the signature using `cosign verify`.
+
+```bash
+cosign verify "$IMG" \
+    --certificate-identity-regexp "$ID_REGEXP" \
+    --certificate-oidc-issuer "$ISSUER"
+```
+
+### Build provenance & SBOM attestations
+
+```bash
+# Build provenance (predicate type slsa.dev/provenance/v1, this happens to be
+# gh's default if --predicate-type is omitted, but named explicitly here anyway)
+gh attestation verify oci://$IMG --owner cloudscale-ch \
+  --predicate-type https://slsa.dev/provenance/v1
+
+# The provenance claim's actual content: which commit/workflow run produced
+# this image (buildDefinition, runDetails.builder.id):
+gh attestation verify oci://$IMG --owner cloudscale-ch \
+  --predicate-type https://slsa.dev/provenance/v1 \
+  --format json \
+  --jq '.[].verificationResult.statement.predicate'
+
+# SBOM (predicate type spdx.dev/Document/v2.3, must be given explicitly,
+# otherwise gh defaults to provenance and the SBOM is never checked)
+gh attestation verify oci://$IMG --owner cloudscale-ch \
+  --predicate-type https://spdx.dev/Document/v2.3
+
+# A verified copy of the SBOM's actual content, extracted from the checked
+# attestation rather than trusted from the release asset on its own:
+gh attestation verify oci://$IMG --owner cloudscale-ch \
+  --predicate-type https://spdx.dev/Document/v2.3 \
+  --format json \
+  --jq '.[].verificationResult.statement.predicate'
+
+# Everything attached at once:
+cosign tree "$IMG"
+```
+
+`sbom.spdx.json` is also attached to the GitHub release directly, but that copy isn't
+independently verifiable as a standalone file: its attestation's subject is the image,
+not the file. The SBOM extraction command above prints the verified content instead.
+
+### Release manifests
+
+Unlike the image, these are plain files with no registry to push into, so
+`cosign sign-blob` produces `checksums.txt.bundle` as a standalone file instead. Both
+checks below matter: `shasum` proves your files match `checksums.txt`; the signature
+proves `checksums.txt` itself is genuine. Either alone isn't enough.
+
+```bash
+cd "$(mktemp -d)"
+gh release download "$TAG" \
+  -R cloudscale-ch/cluster-api-provider-cloudscale \
+  -p 'checksums.txt' \
+  -p 'checksums.txt.bundle' \
+  -p '*.yaml'
+
+# Files match their checksums. `shasum` ships by default on macOS and Linux;
+# GNU coreutils users can use `sha256sum -c` instead (BSD sha256sum's -c compares
+# against a single digest string, not a checksum file).
+shasum -a 256 -c checksums.txt
+
+# checksums.txt itself is signed (predicate type sigstore.dev/cosign/sign/v1). The
+# bundle is a self-describing Sigstore bundle: signature + certificate +
+# transparency-log proof.
+cosign verify-blob \
+  --bundle checksums.txt.bundle \
+  --certificate-identity-regexp "$ID_REGEXP" \
+  --certificate-oidc-issuer "$ISSUER" \
+  checksums.txt
+
+# Each manifest also carries its own build provenance (predicate type
+# slsa.dev/provenance/v1, gh's default, named explicitly here anyway):
+for f in *.yaml; do
+  gh attestation verify "$f" --owner cloudscale-ch \
+    --predicate-type https://slsa.dev/provenance/v1
+done
+```
diff --git a/go.mod b/go.mod
index ec891c8..bce90ae 100644
--- a/go.mod
+++ b/go.mod
@@ -1,6 +1,6 @@
 module github.com/cloudscale-ch/cluster-api-provider-cloudscale
 
-go 1.26.0
+go 1.26.5
 
 require (
 	github.com/cloudscale-ch/cloudscale-go-sdk/v9 v9.1.0