diff --git a/.github/workflows/nightly.yml b/.github/workflows/nightly.yml
index 56125da..7e86b0c 100644
--- a/.github/workflows/nightly.yml
+++ b/.github/workflows/nightly.yml
@@ -42,3 +42,51 @@ jobs:
         TAGS: ghcr.io/edera-dev/${{ matrix.component }}:nightly
         COSIGN_EXPERIMENTAL: "true"
       run: cosign sign --yes "${TAGS}@${DIGEST}"
+
+    - name: Build `build` stage for source-commit capture
+      uses: docker/build-push-action@15560696de535e4014efeff63c48f16952e52dd1 # v6.2.0
+      with:
+        file: ./Dockerfile.${{ matrix.component }}
+        target: build
+        platforms: linux/amd64
+        load: true
+        tags: sbom-scan-${{ matrix.component }}:latest
+    - name: Generate and attest CycloneDX SBOM
+      env:
+        DIGEST: ${{ steps.push-step.outputs.digest }}
+        TAGS: ghcr.io/edera-dev/${{ matrix.component }}:nightly
+        COMPONENT: ${{ matrix.component }}
+        COSIGN_EXPERIMENTAL: "true"
+      run: |
+        set -euo pipefail
+        scan="sbom-scan-${COMPONENT}:latest"
+
+        sha()  { docker run --rm "${scan}" git -C "$1" rev-parse HEAD; }
+        desc() { docker run --rm "${scan}" git -C "$1" describe --tags --always; }
+        case "${COMPONENT}" in
+          squashfs-tools)
+            SQUASHFS_TOOLS_COMMIT="$(sha /usr/src/squashfs-tools)"
+            SQUASHFS_TOOLS_VERSION="$(desc /usr/src/squashfs-tools)"
+            ZLIB_NG_COMMIT="$(sha /usr/src/zlib-ng)"
+            ZLIB_NG_VERSION="$(desc /usr/src/zlib-ng)"
+            export SQUASHFS_TOOLS_COMMIT SQUASHFS_TOOLS_VERSION \
+                   ZLIB_NG_COMMIT ZLIB_NG_VERSION
+            ;;
+          mkfs)
+            E2FSPROGS_COMMIT="$(sha /usr/src/e2fsprogs)"
+            E2FSPROGS_VERSION="$(desc /usr/src/e2fsprogs)"
+            export E2FSPROGS_COMMIT E2FSPROGS_VERSION
+            ;;
+        esac
+
+        python3 generate-sbom.py
+
+        jq -e '.bomFormat == "CycloneDX" and ((.components // []) | length > 0)' \
+          "${COMPONENT}.cdx.json" >/dev/null \
+          || { echo "::error::SBOM for ${COMPONENT} is empty or invalid"; exit 1; }
+        jq '{component: env.COMPONENT, components: (.components | length)}' \
+          "${COMPONENT}.cdx.json"
+
+        cosign attest --yes --type cyclonedx \
+          --predicate "${COMPONENT}.cdx.json" \
+          "${TAGS}@${DIGEST}"
diff --git a/generate-sbom.py b/generate-sbom.py
new file mode 100644
index 0000000..a6c44bd
--- /dev/null
+++ b/generate-sbom.py
@@ -0,0 +1,135 @@
+#!/usr/bin/env python3
+"""Generate a curated CycloneDX SBOM for a published linux-utils-oci image.
+
+Reads from the environment (set by the SBOM workflow step, resolved from the
+build-stage image):
+  COMPONENT               squashfs-tools | mkfs
+  SQUASHFS_TOOLS_COMMIT   resolved commit of plougher/squashfs-tools
+  SQUASHFS_TOOLS_VERSION  git-describe of same
+  ZLIB_NG_COMMIT          resolved commit of zlib-ng/zlib-ng
+  ZLIB_NG_VERSION         git-describe of same
+  E2FSPROGS_COMMIT        resolved commit of e2fsprogs
+  E2FSPROGS_VERSION       git-describe of same (the build-discovered release tag)
+
+Writes <COMPONENT>.cdx.json (CycloneDX 1.6) in the current directory.
+"""
+import json
+import os
+import sys
+
+
+def github_source(name, gh_path, commit, version, ctype="application"):
+    """A GitHub-hosted source component, pinned to commit in its purl."""
+    purl = "pkg:github/%s" % gh_path
+    if commit:
+        purl = "%s@%s" % (purl, commit)
+    component = {
+        "bom-ref": purl,
+        "type": ctype,
+        "name": name,
+        "purl": purl,
+        "externalReferences": [
+            {"type": "vcs", "url": "https://github.com/%s.git" % gh_path}
+        ],
+    }
+    if version:
+        component["version"] = version
+    return component
+
+
+def e2fsprogs_source(commit, version):
+    """e2fsprogs lives on git.kernel.org (not GitHub), so it is a pkg:generic
+    component with the commit carried as a property (purls for generic sources
+    have no standard commit qualifier)."""
+    purl = "pkg:generic/e2fsprogs"
+    if version:
+        purl = "%s@%s" % (purl, version)
+    component = {
+        "bom-ref": purl,
+        "type": "application",
+        "name": "e2fsprogs",
+        "purl": purl,
+        "externalReferences": [
+            {
+                "type": "vcs",
+                "url": "https://git.kernel.org/pub/scm/fs/ext2/e2fsprogs.git",
+            }
+        ],
+    }
+    if version:
+        component["version"] = version
+    if commit:
+        component["properties"] = [
+            {"name": "dev.edera.source.commit", "value": commit}
+        ]
+    return component
+
+
+def build_sources(comp):
+    if comp == "squashfs-tools":
+        return [
+            github_source(
+                "squashfs-tools",
+                "plougher/squashfs-tools",
+                os.environ.get("SQUASHFS_TOOLS_COMMIT", ""),
+                os.environ.get("SQUASHFS_TOOLS_VERSION", ""),
+            ),
+            # zlib-ng is built static (zlib-compat) and linked into the binaries.
+            github_source(
+                "zlib-ng",
+                "zlib-ng/zlib-ng",
+                os.environ.get("ZLIB_NG_COMMIT", ""),
+                os.environ.get("ZLIB_NG_VERSION", ""),
+                ctype="library",
+            ),
+        ]
+    if comp == "mkfs":
+        return [
+            e2fsprogs_source(
+                os.environ.get("E2FSPROGS_COMMIT", ""),
+                os.environ.get("E2FSPROGS_VERSION", ""),
+            )
+        ]
+    print("ERROR: unknown COMPONENT %r" % comp, file=sys.stderr)
+    sys.exit(1)
+
+
+def main():
+    comp = os.environ["COMPONENT"]
+    sources = build_sources(comp)
+
+    image_ref = "%s@nightly" % comp
+    document = {
+        "bomFormat": "CycloneDX",
+        "specVersion": "1.6",
+        "version": 1,
+        "metadata": {
+            "component": {
+                "bom-ref": image_ref,
+                "type": "container",
+                "name": comp,
+            }
+        },
+        "components": sources,
+        "dependencies": [
+            {
+                "ref": image_ref,
+                "dependsOn": [c["bom-ref"] for c in sources if c.get("bom-ref")],
+            }
+        ],
+    }
+
+    with open("%s.cdx.json" % comp, "w") as out:
+        json.dump(document, out, indent=2)
+        out.write("\n")
+
+    print(
+        json.dumps(
+            {"component": comp, "components": len(sources)},
+            indent=2,
+        )
+    )
+
+
+if __name__ == "__main__":
+    main()