diff --git a/toolkit/types/cvss/cvss.go b/toolkit/types/cvss/cvss.go
index 88bd9d923..7a6333242 100644
--- a/toolkit/types/cvss/cvss.go
+++ b/toolkit/types/cvss/cvss.go
@@ -121,21 +121,38 @@ func mkRevLookup[M Metric]() map[string]M {
 //
 // The [Vector.getString] method is used here.
 func marshalVector[M Metric, V Vector[M]](prefix string, v V) ([]byte, error) {
-	text := append(make([]byte, 0, 64), prefix...)
-	for i := 0; i < M(0).num(); i++ {
-		m := M(i)
-		val, err := v.getString(m)
-		switch {
-		case errors.Is(err, nil):
-		case errors.Is(err, errValueUnset):
-			continue
-		default:
-			return nil, errors.New("invalid cvss vector")
+	text := append(make([]byte, 0, 64), prefix...) // Guess at an initial capacity.
+	var err error
+	// This is a rangefunc-style iterator.
+	v.groups(func(b [2]int) bool {
+		var set bool
+		orig := len(text)
+		for i := b[0]; i < b[1]; i++ {
+			m := M(i)
+			val, err := v.getString(m)
+			switch {
+			case errors.Is(err, nil):
+				set = true
+			case errors.Is(err, errValueUnset) && val == "":
+				continue
+			case errors.Is(err, errValueUnset):
+			default:
+				err = errors.New("invalid cvss vector")
+				return false
+			}
+
+			text = append(text, '/')
+			text = append(text, m.String()...)
+			text = append(text, ':')
+			text = append(text, val...)
+		}
+		if !set {
+			text = text[:orig]
 		}
-		text = append(text, '/')
-		text = append(text, m.String()...)
-		text = append(text, ':')
-		text = append(text, val...)
+		return true
+	})
+	if err != nil {
+		return nil, err
 	}
 	// v2 hack
 	if prefix == "" {
diff --git a/toolkit/types/cvss/cvss_v2.go b/toolkit/types/cvss/cvss_v2.go
index 3db6840ee..0b4a32521 100644
--- a/toolkit/types/cvss/cvss_v2.go
+++ b/toolkit/types/cvss/cvss_v2.go
@@ -114,8 +114,11 @@ func (v *V2) String() string {
 // GetString implements [Vector].
 func (v *V2) getString(m V2Metric) (string, error) {
 	b := v.mv[int(m)]
-	if b == 0 {
+	switch {
+	case b == 0 && m <= V2Availability:
 		return "", errValueUnset
+	case b == 0:
+		return "ND", errValueUnset
 	}
 	return v2Unparse(m, b), nil
 }
diff --git a/toolkit/types/cvss/cvss_v2_test.go b/toolkit/types/cvss/cvss_v2_test.go
index 47ac73388..beb6ec01c 100644
--- a/toolkit/types/cvss/cvss_v2_test.go
+++ b/toolkit/types/cvss/cvss_v2_test.go
@@ -19,12 +19,12 @@ func TestV2(t *testing.T) {
 	})
 	t.Run("Roundtrip", func(t *testing.T) {
 		vecs := []string{
-			"AV:N/AC:L/Au:N/C:N/I:N/A:C",                                          // CVE-2002-0392
-			"AV:N/AC:L/Au:N/C:C/I:C/A:C",                                          // CVE-2003-0818
-			"AV:L/AC:H/Au:N/C:C/I:C/A:C",                                          // CVE-2003-0062
-			"AV:L/AC:H/Au:N/C:C/I:C/A:C/E:F/RL:OF/RC:C/CDP:H/TD:H/CR:M/IR:M/AR:H", // CVE-2002-0392
-			"AV:L/AC:H/Au:N/C:C/I:C/A:C/E:F/RL:OF/RC:UR/CDP:ND/TD:ND",             // made up
-			"AV:L/AC:H/Au:N/C:C/I:C/A:C/E:F/RL:OF/RC:UR/CDP:LM/TD:ND",             // made up
+			"AV:N/AC:L/Au:N/C:N/I:N/A:C",                                                // CVE-2002-0392
+			"AV:N/AC:L/Au:N/C:C/I:C/A:C",                                                // CVE-2003-0818
+			"AV:L/AC:H/Au:N/C:C/I:C/A:C",                                                // CVE-2003-0062
+			"AV:L/AC:H/Au:N/C:C/I:C/A:C/E:F/RL:OF/RC:C/CDP:H/TD:H/CR:M/IR:M/AR:H",       // CVE-2002-0392
+			"AV:L/AC:H/Au:N/C:C/I:C/A:C/E:F/RL:OF/RC:UR/CDP:ND/TD:ND/CR:ND/IR:ND/AR:ND", // made up
+			"AV:L/AC:H/Au:N/C:C/I:C/A:C/E:F/RL:OF/RC:UR/CDP:LM/TD:ND/CR:ND/IR:ND/AR:ND", // made up
 		}
 		Roundtrip[V2, V2Metric, *V2](t, vecs)
 	})