diff --git a/build.go b/build.go
index 779b6a27e..fdb6fc481 100644
--- a/build.go
+++ b/build.go
@@ -718,7 +718,7 @@ func shouldBuildSyso(dir string) (string, error) {
 	}
 
 	jsonPath := filepath.Join(dir, "versioninfo.json")
-	err = os.WriteFile(jsonPath, bs, 0o644)
+	err = os.WriteFile(jsonPath, bs, 0o666)
 	if err != nil {
 		return "", errors.New("failed to create " + jsonPath + ": " + err.Error())
 	}
@@ -783,7 +783,7 @@ func copyFile(src, dst string, perm os.FileMode) error {
 	}
 
 copy:
-	os.MkdirAll(filepath.Dir(dst), 0o777)
+	os.MkdirAll(filepath.Dir(dst), os.ModePerm)
 	if err := os.WriteFile(dst, in, perm); err != nil {
 		return err
 	}
@@ -1432,7 +1432,7 @@ func writeCompatJSON() {
 			continue
 		}
 		bs, _ := json.MarshalIndent(e, "", "  ")
-		if err := os.WriteFile("compat.json", bs, 0o644); err != nil {
+		if err := os.WriteFile("compat.json", bs, 0o666); err != nil {
 			log.Fatal("Writing compat.json:", err)
 		}
 		return
diff --git a/cmd/infra/stcrashreceiver/diskstore.go b/cmd/infra/stcrashreceiver/diskstore.go
index 2e3788be7..e13c8bad8 100644
--- a/cmd/infra/stcrashreceiver/diskstore.go
+++ b/cmd/infra/stcrashreceiver/diskstore.go
@@ -42,7 +42,7 @@ type currentFile struct {
 }
 
 func (d *diskStore) Serve(ctx context.Context) {
-	if err := os.MkdirAll(d.dir, 0o700); err != nil {
+	if err := os.MkdirAll(d.dir, os.ModePerm); err != nil {
 		log.Println("Creating directory:", err)
 		return
 	}
@@ -62,7 +62,7 @@ func (d *diskStore) Serve(ctx context.Context) {
 		case entry := <-d.inbox:
 			path := d.fullPath(entry.path)
 
-			if err := os.MkdirAll(filepath.Dir(path), 0o700); err != nil {
+			if err := os.MkdirAll(filepath.Dir(path), os.ModePerm); err != nil {
 				log.Println("Creating directory:", err)
 				continue
 			}
@@ -77,7 +77,7 @@ func (d *diskStore) Serve(ctx context.Context) {
 				log.Println("Failed to compress crash report:", err)
 				continue
 			}
-			if err := os.WriteFile(path, buf.Bytes(), 0o600); err != nil {
+			if err := os.WriteFile(path, buf.Bytes(), 0o666); err != nil {
 				log.Printf("Failed to write %s: %v", entry.path, err)
 				_ = os.Remove(path)
 				continue
diff --git a/cmd/infra/stcrashreceiver/util.go b/cmd/infra/stcrashreceiver/util.go
index ad58b5caa..f0d5b4ccc 100644
--- a/cmd/infra/stcrashreceiver/util.go
+++ b/cmd/infra/stcrashreceiver/util.go
@@ -52,5 +52,5 @@ func compressAndWrite(bs []byte, fullPath string) error {
 	gw.Close()
 
 	// Create an output file with the compressed report
-	return os.WriteFile(fullPath, buf.Bytes(), 0o644)
+	return os.WriteFile(fullPath, buf.Bytes(), 0o666)
 }
diff --git a/cmd/infra/strelaypoolsrv/main.go b/cmd/infra/strelaypoolsrv/main.go
index 0871d5982..fee62dbda 100644
--- a/cmd/infra/strelaypoolsrv/main.go
+++ b/cmd/infra/strelaypoolsrv/main.go
@@ -612,7 +612,7 @@ func saveRelays(file string, relays []*relay) error {
 	for _, relay := range relays {
 		content += relay.uri.String() + "\n"
 	}
-	return os.WriteFile(file, []byte(content), 0o777)
+	return os.WriteFile(file, []byte(content), 0o666)
 }
 
 func createTestCertificate() tls.Certificate {
diff --git a/cmd/syncthing/decrypt/decrypt.go b/cmd/syncthing/decrypt/decrypt.go
index 4545e119c..862566a85 100644
--- a/cmd/syncthing/decrypt/decrypt.go
+++ b/cmd/syncthing/decrypt/decrypt.go
@@ -167,7 +167,7 @@ func (c *CLI) process(srcFs fs.Filesystem, dstFs fs.Filesystem, path string) err
 
 	var plainFd fs.File
 	if dstFs != nil {
-		if err := dstFs.MkdirAll(filepath.Dir(plainFi.Name), 0o700); err != nil {
+		if err := dstFs.MkdirAll(filepath.Dir(plainFi.Name), fs.ModePerm); err != nil {
 			return fmt.Errorf("%s: %w", plainFi.Name, err)
 		}
 
diff --git a/cmd/syncthing/main.go b/cmd/syncthing/main.go
index bd35c6667..35ed25c34 100644
--- a/cmd/syncthing/main.go
+++ b/cmd/syncthing/main.go
@@ -673,7 +673,7 @@ func auditWriter(auditFile string) io.Writer {
 		} else {
 			auditFlags = os.O_WRONLY | os.O_CREATE | os.O_APPEND
 		}
-		fd, err = os.OpenFile(auditFile, auditFlags, 0o600)
+		fd, err = os.OpenFile(auditFile, auditFlags, 0o666)
 		if err != nil {
 			slog.Error("Failed to open audit file", slogutil.Error(err))
 			os.Exit(svcutil.ExitError.AsInt())
diff --git a/cmd/syncthing/monitor.go b/cmd/syncthing/monitor.go
index 35f98600b..7b0cf2186 100644
--- a/cmd/syncthing/monitor.go
+++ b/cmd/syncthing/monitor.go
@@ -479,7 +479,7 @@ func (f *autoclosedFile) ensureOpenLocked() error {
 	// We open the file for write only, and create it if it doesn't exist.
 	flags := os.O_WRONLY | os.O_CREATE | os.O_APPEND
 
-	fd, err := os.OpenFile(f.name, flags, 0o644)
+	fd, err := os.OpenFile(f.name, flags, 0o666)
 	if err != nil {
 		return err
 	}
diff --git a/lib/api/api.go b/lib/api/api.go
index dfdfacc36..046ad33f2 100644
--- a/lib/api/api.go
+++ b/lib/api/api.go
@@ -1248,7 +1248,7 @@ func (s *service) getSupportBundle(w http.ResponseWriter, r *http.Request) {
 	zipFilePath := filepath.Join(locations.GetBaseDir(locations.ConfigBaseDir), zipFileName)
 
 	// Write buffer zip to local zip file (back up)
-	if err := os.WriteFile(zipFilePath, zipFilesBuffer.Bytes(), 0o600); err != nil {
+	if err := os.WriteFile(zipFilePath, zipFilesBuffer.Bytes(), 0o666); err != nil {
 		slog.Warn("Failed to create support bundle zip (file)", slogutil.FilePath(zipFilePath), slogutil.Error(err))
 	}
 
diff --git a/lib/config/folderconfiguration.go b/lib/config/folderconfiguration.go
index 10c8a2776..a2ed4e5ae 100644
--- a/lib/config/folderconfiguration.go
+++ b/lib/config/folderconfiguration.go
@@ -168,7 +168,7 @@ func (f *FolderConfiguration) CreateMarker() error {
 	ffs := f.Filesystem()
 
 	// Create the marker as a directory
-	err := ffs.Mkdir(DefaultMarkerName, 0o755)
+	err := ffs.Mkdir(DefaultMarkerName, fs.ModePerm)
 	if err != nil {
 		return err
 	}
@@ -176,7 +176,7 @@ func (f *FolderConfiguration) CreateMarker() error {
 	// Create a file inside it, reducing the risk of the marker directory
 	// being removed by automated cleanup tools.
 	markerFile := filepath.Join(DefaultMarkerName, f.markerFilename())
-	if err := fs.WriteFile(ffs, markerFile, f.markerContents(), 0o644); err != nil {
+	if err := fs.WriteFile(ffs, markerFile, f.markerContents(), 0o666); err != nil {
 		return err
 	}
 
@@ -246,19 +246,10 @@ func (f *FolderConfiguration) checkFilesystemPath(ffs fs.Filesystem, path string
 }
 
 func (f *FolderConfiguration) CreateRoot() (err error) {
-	// Directory permission bits. Will be filtered down to something
-	// sane by umask on Unixes.
-	permBits := fs.FileMode(0o777)
-	if build.IsWindows {
-		// Windows has no umask so we must chose a safer set of bits to
-		// begin with.
-		permBits = 0o700
-	}
-
 	filesystem := f.Filesystem()
 
 	if _, err = filesystem.Stat("."); fs.IsNotExist(err) {
-		err = filesystem.MkdirAll(".", permBits)
+		err = filesystem.MkdirAll(".", fs.ModePerm)
 	}
 
 	return err
diff --git a/lib/config/migrations.go b/lib/config/migrations.go
index 382bccfad..d237e8a00 100644
--- a/lib/config/migrations.go
+++ b/lib/config/migrations.go
@@ -18,7 +18,6 @@ import (
 	"sync"
 
 	"github.com/syncthing/syncthing/internal/slogutil"
-	"github.com/syncthing/syncthing/lib/build"
 	"github.com/syncthing/syncthing/lib/fs"
 	"github.com/syncthing/syncthing/lib/netutil"
 	"github.com/syncthing/syncthing/lib/upgrade"
@@ -224,27 +223,20 @@ func migrateToConfigV24(cfg *Configuration) {
 }
 
 func migrateToConfigV23(cfg *Configuration) {
-	permBits := fs.FileMode(0o777)
-	if build.IsWindows {
-		// Windows has no umask so we must chose a safer set of bits to
-		// begin with.
-		permBits = 0o700
-	}
-
 	// Upgrade code remains hardcoded for .stfolder despite configurable
 	// marker name in later versions.
 
 	for i := range cfg.Folders {
-		fs := cfg.Folders[i].Filesystem()
+		ffs := cfg.Folders[i].Filesystem()
 		// Invalid config posted, or tests.
-		if fs == nil {
+		if ffs == nil {
 			continue
 		}
-		if stat, err := fs.Stat(DefaultMarkerName); err == nil && !stat.IsDir() {
-			err = fs.Remove(DefaultMarkerName)
+		if stat, err := ffs.Stat(DefaultMarkerName); err == nil && !stat.IsDir() {
+			err = ffs.Remove(DefaultMarkerName)
 			if err == nil {
-				err = fs.Mkdir(DefaultMarkerName, permBits)
-				fs.Hide(DefaultMarkerName) // ignore error
+				err = ffs.Mkdir(DefaultMarkerName, fs.ModePerm)
+				ffs.Hide(DefaultMarkerName) // ignore error
 			}
 			if err != nil {
 				slog.Warn("Failed to upgrade folder marker", slogutil.Error(err))
diff --git a/lib/fs/basicfs.go b/lib/fs/basicfs.go
index d5a01184f..cf40f6fc8 100644
--- a/lib/fs/basicfs.go
+++ b/lib/fs/basicfs.go
@@ -174,7 +174,7 @@ func (f *BasicFilesystem) MkdirAll(path string, perm FileMode) error {
 		return err
 	}
 
-	return f.mkdirAll(path, os.FileMode(perm))
+	return os.MkdirAll(path, os.FileMode(perm))
 }
 
 func (f *BasicFilesystem) Lstat(name string) (FileInfo, error) {
diff --git a/lib/fs/basicfs_unix.go b/lib/fs/basicfs_unix.go
index c60e67574..dc0f963ce 100644
--- a/lib/fs/basicfs_unix.go
+++ b/lib/fs/basicfs_unix.go
@@ -32,10 +32,6 @@ func (f *BasicFilesystem) ReadSymlink(name string) (string, error) {
 	return os.Readlink(name)
 }
 
-func (*BasicFilesystem) mkdirAll(path string, perm os.FileMode) error {
-	return os.MkdirAll(path, perm)
-}
-
 // Unhide is a noop on unix, as unhiding files requires renaming them.
 // We still check that the relative path does not try to escape the root
 func (f *BasicFilesystem) Unhide(name string) error {
diff --git a/lib/fs/basicfs_windows.go b/lib/fs/basicfs_windows.go
index d1b8d88c2..34c3bb860 100644
--- a/lib/fs/basicfs_windows.go
+++ b/lib/fs/basicfs_windows.go
@@ -31,57 +31,6 @@ func (BasicFilesystem) CreateSymlink(target, name string) error {
 	return errNotSupported
 }
 
-// Required due to https://github.com/golang/go/issues/10900
-func (f *BasicFilesystem) mkdirAll(path string, perm os.FileMode) error {
-	// Fast path: if we can tell whether path is a directory or file, stop with success or error.
-	dir, err := os.Stat(path)
-	if err == nil {
-		if dir.IsDir() {
-			return nil
-		}
-		return &os.PathError{
-			Op:   "mkdir",
-			Path: path,
-			Err:  syscall.ENOTDIR,
-		}
-	}
-
-	// Slow path: make sure parent exists and then call Mkdir for path.
-	i := len(path)
-	for i > 0 && IsPathSeparator(path[i-1]) { // Skip trailing path separator.
-		i--
-	}
-
-	j := i
-	for j > 0 && !IsPathSeparator(path[j-1]) { // Scan backward over element.
-		j--
-	}
-
-	if j > 1 {
-		// Create parent
-		parent := path[0 : j-1]
-		if parent != filepath.VolumeName(parent) {
-			err = f.mkdirAll(parent, perm)
-			if err != nil {
-				return err
-			}
-		}
-	}
-
-	// Parent now exists; invoke Mkdir and use its result.
-	err = os.Mkdir(path, perm)
-	if err != nil {
-		// Handle arguments like "foo/." by
-		// double-checking that directory doesn't exist.
-		dir, err1 := os.Lstat(path)
-		if err1 == nil && dir.IsDir() {
-			return nil
-		}
-		return err
-	}
-	return nil
-}
-
 func (f *BasicFilesystem) Unhide(name string) error {
 	name, err := f.rooted(name)
 	if err != nil {
diff --git a/lib/fs/fakefs.go b/lib/fs/fakefs.go
index ef0ccd7c5..ff69dfd32 100644
--- a/lib/fs/fakefs.go
+++ b/lib/fs/fakefs.go
@@ -153,7 +153,7 @@ func newFakeFilesystem(rootURI string, _ ...Option) *fakeFS {
 		for (files == 0 || createdFiles < files) && (maxsize == 0 || writtenData>>20 < int64(maxsize)) {
 			dir := filepath.Join(fmt.Sprintf("%02x", rng.Intn(255)), fmt.Sprintf("%02x", rng.Intn(255)))
 			file := fmt.Sprintf("%016x", rng.Int63())
-			_ = fs.MkdirAll(dir, 0o755)
+			_ = fs.MkdirAll(dir, ModePerm)
 
 			fd, _ := fs.Create(filepath.Join(dir, file))
 			createdFiles++
@@ -169,7 +169,7 @@ func newFakeFilesystem(rootURI string, _ ...Option) *fakeFS {
 
 	if !nostfolder {
 		// Also create a default folder marker for good measure
-		_ = fs.Mkdir(".stfolder", 0o700)
+		_ = fs.Mkdir(".stfolder", ModePerm)
 	}
 
 	// We only set the latency after doing the operations required to create
diff --git a/lib/model/folder_sendrecv.go b/lib/model/folder_sendrecv.go
index c13024f52..b9ea673c4 100644
--- a/lib/model/folder_sendrecv.go
+++ b/lib/model/folder_sendrecv.go
@@ -701,7 +701,7 @@ func (f *sendReceiveFolder) checkParent(file string, scanChan chan<- string) boo
 		return true
 	}
 	f.sl.Debug("Creating parent directory", slogutil.FilePath(file))
-	if err := f.mtimefs.MkdirAll(parent, 0o755); err != nil {
+	if err := f.mtimefs.MkdirAll(parent, fs.ModePerm); err != nil {
 		f.newPullError(file, fmt.Errorf("creating parent dir: %w", err))
 		return false
 	}
diff --git a/lib/model/model.go b/lib/model/model.go
index 4c82a81eb..a57bd23ab 100644
--- a/lib/model/model.go
+++ b/lib/model/model.go
@@ -1784,7 +1784,7 @@ func (m *model) handleAutoAccepts(deviceID protocol.DeviceID, folder protocol.Fo
 
 			// Attempt to create it to make sure it does, now.
 			fullPath := filepath.Join(defaultFolderCfg.Path, path)
-			if err := defaultPathFs.MkdirAll(path, 0o700); err != nil {
+			if err := defaultPathFs.MkdirAll(path, fs.ModePerm); err != nil {
 				slog.Error("Failed to create path for auto-accepted folder", folder.LogAttr(), slogutil.FilePath(fullPath), slogutil.Error(err))
 				continue
 			}
diff --git a/lib/versioner/util.go b/lib/versioner/util.go
index 221de5dc5..dc2e723ad 100644
--- a/lib/versioner/util.go
+++ b/lib/versioner/util.go
@@ -155,7 +155,7 @@ func archiveFile(method fs.CopyRangeMethod, srcFs, dstFs fs.Filesystem, filePath
 	if err != nil {
 		if fs.IsNotExist(err) {
 			slog.Debug("Creating versions dir")
-			err := dstFs.MkdirAll(".", 0o755)
+			err := dstFs.MkdirAll(".", fs.ModePerm)
 			if err != nil {
 				return err
 			}
@@ -328,7 +328,7 @@ func restoreFile(method fs.CopyRangeMethod, src, dst fs.Filesystem, filePath str
 		return err
 	}
 
-	_ = dst.MkdirAll(filepath.Dir(filePath), 0o755)
+	_ = dst.MkdirAll(filepath.Dir(filePath), fs.ModePerm)
 	err := osutil.RenameOrCopy(method, src, dst, sourceFile, filePath)
 	_ = dst.Chtimes(filePath, sourceMtime, sourceMtime)
 	return err
diff --git a/script/authors.go b/script/authors.go
index 23865cc1f..cdb3fa4d1 100644
--- a/script/authors.go
+++ b/script/authors.go
@@ -93,7 +93,7 @@ func main() {
 	}
 	bs = authorsRe.ReplaceAll(bs, []byte("id=\"contributor-list\">\n"+replacement+"\n          </div>"))
 
-	if err := os.WriteFile(htmlFile, bs, 0o644); err != nil {
+	if err := os.WriteFile(htmlFile, bs, 0o666); err != nil {
 		log.Fatal(err)
 	}
 
diff --git a/script/copyrights.go b/script/copyrights.go
index 89a78833e..8c2b4f37e 100644
--- a/script/copyrights.go
+++ b/script/copyrights.go
@@ -265,7 +265,7 @@ func readAll(path string) []byte {
 }
 
 func writeFile(path string, data string) {
-	err := os.WriteFile(path, []byte(data), 0o644)
+	err := os.WriteFile(path, []byte(data), 0o666)
 	if err != nil {
 		log.Fatal(err)
 	}