3 files changed, 23 insertions, 14 deletions
diff --git a/src/path/filepath/path.go b/src/path/filepath/path.go
index a6578cbb72..32dd887998 100644
--- a/src/path/filepath/path.go
+++ b/src/path/filepath/path.go
@@ -15,6 +15,7 @@ import (
 	"errors"
 	"io/fs"
 	"os"
+	"runtime"
 	"sort"
 	"strings"
 )
@@ -117,21 +118,9 @@ func Clean(path string) string {
 		case os.IsPathSeparator(path[r]):
 			// empty path element
 			r++
-		case path[r] == '.' && r+1 == n:
+		case path[r] == '.' && (r+1 == n || os.IsPathSeparator(path[r+1])):
 			// . element
 			r++
-		case path[r] == '.' && os.IsPathSeparator(path[r+1]):
-			// ./ element
-			r++
-
-			for r < len(path) && os.IsPathSeparator(path[r]) {
-				r++
-			}
-			if out.w == 0 && volumeNameLen(path[r:]) > 0 {
-				// When joining prefix "." and an absolute path on Windows,
-				// the prefix should not be removed.
-				out.append('.')
-			}
 		case path[r] == '.' && path[r+1] == '.' && (r+2 == n || os.IsPathSeparator(path[r+2])):
 			// .. element: remove to last separator
 			r += 2
@@ -157,6 +146,18 @@ func Clean(path string) string {
 			if rooted && out.w != 1 || !rooted && out.w != 0 {
 				out.append(Separator)
 			}
+			// If a ':' appears in the path element at the start of a Windows path,
+			// insert a .\ at the beginning to avoid converting relative paths
+			// like a/../c: into c:.
+			if runtime.GOOS == "windows" && out.w == 0 && out.volLen == 0 && r != 0 {
+				for i := r; i < n && !os.IsPathSeparator(path[i]); i++ {
+					if path[i] == ':' {
+						out.append('.')
+						out.append(Separator)
+						break
+					}
+				}
+			}
 			// copy element
 			for ; r < n && !os.IsPathSeparator(path[r]); r++ {
 				out.append(path[r])
diff --git a/src/path/filepath/path_test.go b/src/path/filepath/path_test.go
index 672d7e6261..9adf641013 100644
--- a/src/path/filepath/path_test.go
+++ b/src/path/filepath/path_test.go
@@ -106,6 +106,13 @@ var wincleantests = []PathTest{
 	{`//abc`, `\\abc`},
 	{`///abc`, `\\\abc`},
 	{`//abc//`, `\\abc\\`},
+
+	// Don't allow cleaning to move an element with a colon to the start of the path.
+	{`a/../c:`, `.\c:`},
+	{`a\..\c:`, `.\c:`},
+	{`a/../c:/a`, `.\c:\a`},
+	{`a/../../c:`, `..\c:`},
+	{`foo:bar`, `foo:bar`},
 }
 
 func TestClean(t *testing.T) {
@@ -174,6 +181,7 @@ var winislocaltests = []IsLocalTest{
 	{`C:`, false},
 	{`C:\a`, false},
 	{`..\a`, false},
+	{`a/../c:`, false},
 	{`CONIN$`, false},
 	{`conin$`, false},
 	{`CONOUT$`, false},
diff --git a/src/path/filepath/path_windows_test.go b/src/path/filepath/path_windows_test.go
index 8553485a2d..42aeb4f619 100644
--- a/src/path/filepath/path_windows_test.go
+++ b/src/path/filepath/path_windows_test.go
@@ -548,7 +548,7 @@ func TestIssue52476(t *testing.T) {
 	}{
 		{`..\.`, `C:`, `..\C:`},
 		{`..`, `C:`, `..\C:`},
-		{`.`, `:`, `:`},
+		{`.`, `:`, `.\:`},
 		{`.`, `C:`, `.\C:`},
 		{`.`, `C:/a/b/../c`, `.\C:\a\c`},
 		{`.`, `\C:`, `.\C:`},