2 files changed, 71 insertions, 0 deletions
diff --git a/src/net/url/url.go b/src/net/url/url.go
index 3acd202c24..202957a3a2 100644
--- a/src/net/url/url.go
+++ b/src/net/url/url.go
@@ -929,7 +929,30 @@ func ParseQuery(query string) (Values, error) {
 	return m, err
 }
 
+var urlmaxqueryparams = godebug.New("urlmaxqueryparams")
+
+const defaultMaxParams = 10000
+
+func urlParamsWithinMax(params int) bool {
+	withinDefaultMax := params <= defaultMaxParams
+	if urlmaxqueryparams.Value() == "" {
+		return withinDefaultMax
+	}
+	customMax, err := strconv.Atoi(urlmaxqueryparams.Value())
+	if err != nil {
+		return withinDefaultMax
+	}
+	withinCustomMax := customMax == 0 || params < customMax
+	if withinDefaultMax != withinCustomMax {
+		urlmaxqueryparams.IncNonDefault()
+	}
+	return withinCustomMax
+}
+
 func parseQuery(m Values, query string) (err error) {
+	if !urlParamsWithinMax(strings.Count(query, "&") + 1) {
+		return errors.New("number of URL query parameters exceeded limit")
+	}
 	for query != "" {
 		var key string
 		key, query, _ = strings.Cut(query, "&")
diff --git a/src/net/url/url_test.go b/src/net/url/url_test.go
index bb48bb6bee..d099353eb2 100644
--- a/src/net/url/url_test.go
+++ b/src/net/url/url_test.go
@@ -1521,6 +1521,54 @@ func TestParseQuery(t *testing.T) {
 	}
 }
 
+func TestParseQueryLimits(t *testing.T) {
+	for _, test := range []struct {
+		params  int
+		godebug string
+		wantErr bool
+	}{{
+		params:  10,
+		wantErr: false,
+	}, {
+		params:  defaultMaxParams,
+		wantErr: false,
+	}, {
+		params:  defaultMaxParams + 1,
+		wantErr: true,
+	}, {
+		params:  10,
+		godebug: "urlmaxqueryparams=9",
+		wantErr: true,
+	}, {
+		params:  defaultMaxParams + 1,
+		godebug: "urlmaxqueryparams=0",
+		wantErr: false,
+	}} {
+		t.Setenv("GODEBUG", test.godebug)
+		want := Values{}
+		var b strings.Builder
+		for i := range test.params {
+			if i > 0 {
+				b.WriteString("&")
+			}
+			p := fmt.Sprintf("p%v", i)
+			b.WriteString(p)
+			want[p] = []string{""}
+		}
+		query := b.String()
+		got, err := ParseQuery(query)
+		if gotErr, wantErr := err != nil, test.wantErr; gotErr != wantErr {
+			t.Errorf("GODEBUG=%v ParseQuery(%v params) = %v, want error: %v", test.godebug, test.params, err, wantErr)
+		}
+		if err != nil {
+			continue
+		}
+		if got, want := len(got), test.params; got != want {
+			t.Errorf("GODEBUG=%v ParseQuery(%v params): got %v params, want %v", test.godebug, test.params, got, want)
+		}
+	}
+}
+
 type RequestURITest struct {
 	url *URL
 	out string