diff --git a/.github/actions/build-shared/action.yml b/.github/actions/build-shared/action.yml
new file mode 100644
index 00000000000000..6ad127da461967
--- /dev/null
+++ b/.github/actions/build-shared/action.yml
@@ -0,0 +1,72 @@
+name: Build Node.js (shared libraries)
+description: >
+  Downloads the slim tarball built by the `build-tarball` job, extracts it,
+  installs Nix (+ cachix + sccache), then builds Node.js and runs the CI
+  test suite inside the pinned nix-shell.
+
+inputs:
+  system:
+    description: System label (e.g. x86_64-linux, aarch64-darwin).
+    required: true
+  extra-nix-args:
+    description: Additional arguments appended to the nix-shell invocation.
+    required: false
+    default: ''
+  cachix-auth-token:
+    description: Cachix auth token for nodejs.cachix.org.
+    required: false
+    default: ''
+
+runs:
+  using: composite
+  steps:
+    - uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c  # v8.0.1
+      if: ${{ github.event_name != 'workflow_dispatch' }}
+      with:
+        name: tarballs
+        path: tarballs
+
+    - name: Extract tarball
+      if: ${{ github.event_name != 'workflow_dispatch' }}
+      shell: bash
+      run: |
+        tar xzf tarballs/*.tar.gz -C "$RUNNER_TEMP"
+        echo "TAR_DIR=$RUNNER_TEMP/$(basename tarballs/*.tar.gz .tar.gz)" >> "$GITHUB_ENV"
+
+    - uses: cachix/install-nix-action@96951a368ba55167b55f1c916f7d416bac6505fe  # v31.10.3
+      with:
+        extra_nix_config: sandbox = true
+
+    - uses: cachix/cachix-action@1eb2ef646ac0255473d23a5907ad7b04ce94065c  # v17
+      with:
+        name: nodejs
+        authToken: ${{ inputs.cachix-auth-token }}
+
+    - name: Configure sccache
+      if: github.base_ref == 'main' || github.ref_name == 'main'
+      uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd  # v8.0.0
+      with:
+        script: |
+          core.exportVariable('SCCACHE_GHA_ENABLED', 'on');
+          core.exportVariable('ACTIONS_CACHE_SERVICE_V2', 'on');
+          core.exportVariable('ACTIONS_RESULTS_URL', process.env.ACTIONS_RESULTS_URL || '');
+          core.exportVariable('ACTIONS_RUNTIME_TOKEN', process.env.ACTIONS_RUNTIME_TOKEN || '');
+          core.exportVariable('NIX_SCCACHE', '(import <nixpkgs> {}).sccache');
+
+    - name: Build Node.js and run tests
+      shell: bash
+      run: |
+        nix-shell \
+          -I "nixpkgs=$TAR_DIR/tools/nix/pkgs.nix" \
+          --pure --keep TAR_DIR --keep FLAKY_TESTS \
+          --keep SCCACHE_GHA_ENABLED --keep ACTIONS_CACHE_SERVICE_V2 --keep ACTIONS_RESULTS_URL --keep ACTIONS_RUNTIME_TOKEN \
+          --arg loadJSBuiltinsDynamically false \
+          --arg useSeparateDerivationForV8 true \
+          --arg ccache "${NIX_SCCACHE:-null}" \
+          --arg devTools '[]' \
+          --arg benchmarkTools '[]' \
+          ${{ endsWith(inputs.system, '-darwin') && '--arg withAmaro false --arg withLief false --arg withSQLite false --arg withFFI false --arg extraConfigFlags ''["--without-inspector" "--without-node-options"]'' \' || '\' }}
+          ${{ inputs.extra-nix-args }} \
+          --run '
+              make -C "$TAR_DIR" run-ci -j4 V=1 TEST_CI_ARGS="-p actions --measure-flakiness 9 --skip-tests=$CI_SKIP_TESTS"
+          ' "$TAR_DIR/shell.nix"
diff --git a/.github/workflows/test-shared.yml b/.github/workflows/test-shared.yml
index c746b2d75e9fde..0fbf0e8fc8b02e 100644
--- a/.github/workflows/test-shared.yml
+++ b/.github/workflows/test-shared.yml
@@ -47,6 +47,7 @@ on:
       - vcbuild.bat
       - .**
       - '!.github/workflows/test-shared.yml'
+      - '!.github/actions/build-shared/**'
     types: [opened, synchronize, reopened, ready_for_review]
   push:
     branches:
@@ -97,6 +98,7 @@ on:
       - vcbuild.bat
       - .**
       - '!.github/workflows/test-shared.yml'
+      - '!.github/actions/build-shared/**'
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
@@ -153,50 +155,76 @@ jobs:
     name: '${{ matrix.system }}: with shared libraries'
     runs-on: ${{ matrix.runner }}
     steps:
-      - uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c  # v8.0.1
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
         if: ${{ github.event_name != 'workflow_dispatch' }}
         with:
-          name: tarballs
-          path: tarballs
-
-      - name: Extract tarball
+          persist-credentials: false
+          sparse-checkout: .github/actions
+      - uses: ./.github/actions/build-shared
         if: ${{ github.event_name != 'workflow_dispatch' }}
-        run: |
-          tar xzf tarballs/*.tar.gz -C "$RUNNER_TEMP"
-          echo "TAR_DIR=$RUNNER_TEMP/$(basename tarballs/*.tar.gz .tar.gz)" >> "$GITHUB_ENV"
+        with:
+          system: ${{ matrix.system }}
+          cachix-auth-token: ${{ secrets.CACHIX_AUTH_TOKEN }}
 
+  # Builds the matrix for the `build-openssl` job. The logic lives in
+  # tools/nix/collect-openssl-matrix.sh.
+  # Output shape:
+  # [{ "version": "3.6.1", "attr": "openssl_3_6", "continue-on-error": false }, ...]
+  collect-openssl-versions:
+    if: github.event.pull_request.draft == false
+    runs-on: ubuntu-slim
+    outputs:
+      matrix: ${{ steps.query.outputs.matrix }}
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
+        with:
+          persist-credentials: false
+          sparse-checkout: tools/nix
+          sparse-checkout-cone-mode: false
       - uses: cachix/install-nix-action@96951a368ba55167b55f1c916f7d416bac6505fe  # v31.10.3
         with:
           extra_nix_config: sandbox = true
+      - id: query
+        env:
+          # Latest OpenSSL release we support running tests with. Anything
+          # newer runs with continue-on-error in `build-openssl`.
+          SUPPORTED_OPENSSL_VERSION: '4.0'
+        run: |
+          matrix=$(./tools/nix/collect-openssl-matrix.sh)
+          echo "matrix=$matrix" >> "$GITHUB_OUTPUT"
 
-      - uses: cachix/cachix-action@1eb2ef646ac0255473d23a5907ad7b04ce94065c  # v17
+  # Builds and tests Node.js with shared libraries against every supported
+  # OpenSSL release version available in the repo-pinned nixpkgs. The default
+  # shared `openssl` from tools/nix/sharedLibDeps.nix is overridden per matrix
+  # entry, while all other shared libs remain at their defaults. Only runs on
+  # a single runner/system (aarch64-linux) to keep the matrix to a minimum.
+  build-openssl:
+    needs:
+      - build-tarball
+      - collect-openssl-versions
+    strategy:
+      fail-fast: false
+      matrix:
+        openssl: ${{ fromJSON(needs.collect-openssl-versions.outputs.matrix) }}
+    name: 'aarch64-linux: with shared ${{ matrix.openssl.attr }} (${{ matrix.openssl.version }})'
+    runs-on: ubuntu-24.04-arm
+    continue-on-error: ${{ matrix.openssl['continue-on-error'] }}
+    env:
+      OPENSSL_ATTR: ${{ matrix.openssl.attr }}
+      OPENSSL_VERSION: ${{ matrix.openssl.version }}
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
         with:
-          name: nodejs
-          authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}
-
-      - name: Configure sccache
-        if: github.base_ref == 'main' || github.ref_name == 'main'
-        uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd  # v8.0.0
+          persist-credentials: false
+          sparse-checkout: .github/actions
+      - uses: ./.github/actions/build-shared
         with:
-          script: |
-            core.exportVariable('SCCACHE_GHA_ENABLED', 'on');
-            core.exportVariable('ACTIONS_CACHE_SERVICE_V2', 'on');
-            core.exportVariable('ACTIONS_RESULTS_URL', process.env.ACTIONS_RESULTS_URL || '');
-            core.exportVariable('ACTIONS_RUNTIME_TOKEN', process.env.ACTIONS_RUNTIME_TOKEN || '');
-            core.exportVariable('NIX_SCCACHE', '(import <nixpkgs> {}).sccache');
-
-      - name: Build Node.js and run tests
-        run: |
-          nix-shell \
-            -I "nixpkgs=$TAR_DIR/tools/nix/pkgs.nix" \
-            --pure --keep TAR_DIR --keep FLAKY_TESTS \
-            --keep SCCACHE_GHA_ENABLED --keep ACTIONS_CACHE_SERVICE_V2 --keep ACTIONS_RESULTS_URL --keep ACTIONS_RUNTIME_TOKEN \
-            --arg loadJSBuiltinsDynamically false \
-            --arg useSeparateDerivationForV8 true \
-            --arg ccache "${NIX_SCCACHE:-null}" \
-            --arg devTools '[]' \
-            --arg benchmarkTools '[]' \
-            ${{ endsWith(matrix.system, '-darwin') && '--arg withAmaro false --arg withLief false --arg withSQLite false --arg withFFI false --arg extraConfigFlags ''["--without-inspector" "--without-node-options"]'' \' || '\' }}
-            --run '
-                make -C "$TAR_DIR" run-ci -j4 V=1 TEST_CI_ARGS="-p actions --measure-flakiness 9 --skip-tests=$CI_SKIP_TESTS"
-            ' "$TAR_DIR/shell.nix"
+          system: aarch64-linux
+          cachix-auth-token: ${{ secrets.CACHIX_AUTH_TOKEN }}
+          # Override just the `openssl` attr of the default shared-lib set with
+          # the matrix-selected nixpkgs attribute (e.g. `openssl_3_6`). All
+          # other shared libs (brotli, cares, libuv, …) keep their defaults.
+          # `permittedInsecurePackages` whitelists just the matrix-selected
+          # release (e.g. `openssl-1.1.1w`) so EOL-with-extended-support
+          # cycles evaluate without relaxing nixpkgs' meta check globally.
+          extra-nix-args: --arg sharedLibDeps "(import $TAR_DIR/tools/nix/sharedLibDeps.nix {}) // { openssl = (import $TAR_DIR/tools/nix/pkgs.nix { config.permittedInsecurePackages = [ \"openssl-$OPENSSL_VERSION\" ]; }).$OPENSSL_ATTR; }"
diff --git a/tools/nix/collect-openssl-matrix.sh b/tools/nix/collect-openssl-matrix.sh
new file mode 100755
index 00000000000000..bb2d4ae334b164
--- /dev/null
+++ b/tools/nix/collect-openssl-matrix.sh
@@ -0,0 +1,76 @@
+#!/bin/sh
+#
+# Emits a JSON matrix of OpenSSL releases to test Node.js against with
+# shared libraries, consumed by the `build-openssl` job in
+# .github/workflows/test-shared.yml.
+#
+# Inputs (env):
+#   SUPPORTED_OPENSSL_VERSION  Latest OpenSSL release we support running
+#                              tests with. Anything newer is emitted with
+#                              "continue-on-error": true.
+#
+# Output (stdout): a JSON array with shape
+#   [{ "version": "3.6.1", "attr": "openssl_3_6", "continue-on-error": false }, ...]
+#
+# Usage: SUPPORTED_OPENSSL_VERSION=4.0 ./tools/nix/collect-openssl-matrix.sh
+
+set -eu
+
+: "${SUPPORTED_OPENSSL_VERSION:?SUPPORTED_OPENSSL_VERSION must be set}"
+
+here=$(cd -- "$(dirname -- "$0")" && pwd)
+
+# 1. Enumerate every `openssl_N` / `openssl_N_M` attribute exposed by the
+#    repo-pinned nixpkgs. `tryEval` skips aliases that raise (e.g.
+#    `openssl_3_0` → renamed to `openssl_3`) so we only keep attributes
+#    that resolve to a real derivation with a `.version`.
+nix_json=$(nix-instantiate --eval --strict --json -E "
+  let
+    pkgs = import $here/pkgs.nix {};
+    names = builtins.filter
+      (n: builtins.match \"openssl_[0-9]+(_[0-9]+)?\" n != null)
+      (builtins.attrNames pkgs);
+    safe = builtins.filter (n:
+      let t = builtins.tryEval pkgs.\${n}; in
+      t.success && (builtins.tryEval t.value.version).success) names;
+  in map (n: { attr = n; version = pkgs.\${n}.version; }) safe
+")
+
+# 2. Resolve the OpenSSL version the `build` job already covers (the default
+#    from sharedLibDeps.nix) so we can drop it from the matrix to avoid
+#    duplicate coverage.
+default_openssl_version=$(nix-instantiate --eval --strict --json -E "
+  (import $here/sharedLibDeps.nix {}).openssl.version
+" | jq -r .)
+
+# 3. Fetch OpenSSL release versions from endoflife.date, keep entries that
+#    are either not past EOL or still under extended support, then pick the
+#    first nix attr whose `.version` starts with the release version
+#    followed by `.` / letter / end-of-string (so "3.6" matches "3.6.1",
+#    "1.1.1" matches "1.1.1w", and "1.1" does NOT swallow "1.1.1").
+#    Releases without a matching nix attr and the one covered by default in
+#    `build` are dropped.
+curl -sf https://endoflife.date/api/openssl.json \
+  | jq -c \
+      --argjson nix "$nix_json" \
+      --arg supported "$SUPPORTED_OPENSSL_VERSION" \
+      --arg default_version "$default_openssl_version" '
+    (now | strftime("%Y-%m-%d")) as $today |
+    # Compare two dotted version strings as arrays of numbers
+    # (e.g. "4.1" > "4.0" => true, "4.0" > "4.0" => false).
+    def gt($a; $b):
+      ([$a, $b] | map(split(".") | map(tonumber))) as [$x, $y]
+      | ($x | length) as $n | ($y | length) as $m
+      | [range(0; if $n > $m then $n else $m end)
+          | ((($x[.]) // 0) - (($y[.]) // 0))]
+      | map(select(. != 0)) | (.[0] // 0) > 0;
+    [ .[]
+      | select(.eol == false or .eol > $today or .extendedSupport == true)
+      | .cycle as $v
+      | ($nix
+          | map(select(.version | test("^" + ($v | gsub("\\."; "\\.")) + "([.a-z]|$)")))
+          | first) as $m
+      | select($m != null)
+      | select($m.version != $default_version)
+      | { version: $m.version, attr: $m.attr, "continue-on-error": gt($v; $supported) }
+    ]'