diff --git a/NEWS b/NEWS
index 942a8e9b0651..1e1c1c1bf2f0 100644
--- a/NEWS
+++ b/NEWS
@@ -47,6 +47,10 @@ PHP                                                                        NEWS
   . Fixed password_get_info() and password_needs_rehash() accepting malformed
     bcrypt costs. (Ilia Alshanetsky)
 
+- Windows:
+  . Fixed DOS device prefixed paths not being canonicalized, so junctions were
+    not resolved and open_basedir saw a different path. (Jakub Zelenka)
+
 - Zip:
   . Fixed use-after-free when re-entering ZipArchive during destruction or
     a close warning, and rejected opening streams while closing. (jvoisin)
diff --git a/Zend/zend_virtual_cwd.c b/Zend/zend_virtual_cwd.c
index 48f817310d2a..0a5d41f3dd36 100644
--- a/Zend/zend_virtual_cwd.c
+++ b/Zend/zend_virtual_cwd.c
@@ -1029,6 +1029,22 @@ CWD_API int virtual_file_ex(cwd_state *state, const char *path, verify_path_func
 #endif
 
 #ifdef ZEND_WIN32
+	/* Strip the DOS device prefix from \\.\C:\ and \\?\C:\ paths and rewrite
+	 * \\?\UNC\ paths to \\server\share\, so they resolve like plain paths. */
+	if (path_length > 4 && IS_SLASH(path[0]) && IS_SLASH(path[1])
+			&& (path[2] == '.' || path[2] == '?') && IS_SLASH(path[3])) {
+		if (path_length > 6 && isalpha((unsigned char)path[4]) && path[5] == ':' && IS_SLASH(path[6])) {
+			path += 4;
+			path_length -= 4;
+		} else if (path_length > 8 && strncasecmp(path + 4, "UNC", 3) == 0 && IS_SLASH(path[7])) {
+			resolved_path[0] = DEFAULT_SLASH;
+			resolved_path[1] = DEFAULT_SLASH;
+			memcpy(resolved_path + 2, path + 8, path_length - 8 + 1);
+			path = resolved_path;
+			path_length -= 6;
+		}
+	}
+
 	switch (php_win32_ioutil_path_kind_a(path, path_length)) {
 		case PHP_WIN32_IOUTIL_PATH_RESERVED:
 			SET_ERRNO_FROM_WIN32_CODE(ERROR_INVALID_NAME);
@@ -1103,7 +1119,7 @@ CWD_API int virtual_file_ex(cwd_state *state, const char *path, verify_path_func
 			resolved_path[2] = DEFAULT_SLASH;
 			memcpy(resolved_path + 3, path + 2, path_length - 1);
 			path_length++;
-		} else
+		} else if (path != resolved_path) /* already rewritten from \\?\UNC\ */
 #endif
 		memcpy(resolved_path, path, path_length + 1);
 	}
diff --git a/ext/standard/tests/file/dos_device_prefix-win32.phpt b/ext/standard/tests/file/dos_device_prefix-win32.phpt
new file mode 100644
index 000000000000..74e87f0dbc76
--- /dev/null
+++ b/ext/standard/tests/file/dos_device_prefix-win32.phpt
@@ -0,0 +1,87 @@
+--TEST--
+DOS device prefixed paths resolve junctions and respect open_basedir
+--SKIPIF--
+<?php
+if (substr(PHP_OS, 0, 3) !== "WIN") {
+    die("skip Windows only");
+}
+?>
+--FILE--
+<?php
+
+$sep = DIRECTORY_SEPARATOR;
+$dir = __DIR__ . $sep . 'dos_device_prefix';
+$allowed = $dir . $sep . 'allowed';
+$secret = $dir . $sep . 'secret';
+$junction = $allowed . $sep . 'junction';
+
+mkdir($allowed, 0777, true);
+mkdir($secret);
+file_put_contents($allowed . $sep . 'ok.txt', 'ok');
+file_put_contents($secret . $sep . 'file.txt', 'secret');
+exec(sprintf('mklink /J "%s" "%s"', $junction, $secret), $output, $status);
+if ($status !== 0) {
+    die("mklink failed: " . implode("\n", $output));
+}
+
+$plain = $junction . $sep . 'file.txt';
+$spellings = [
+    'plain' => $plain,
+    'dot' => '\\\\.\\' . $plain,
+    'question' => '\\\\?\\' . $plain,
+];
+$expected = $secret . $sep . 'file.txt';
+
+echo "Junction resolves through all spellings:\n";
+foreach ($spellings as $name => $path) {
+    echo "$name: ";
+    var_dump(realpath($path) === $expected, file_get_contents($path));
+}
+
+echo "Prefixed paths without a drive letter are left alone:\n";
+$h = fopen('\\\\.\\NUL', 'wb');
+var_dump(is_resource($h));
+fclose($h);
+
+echo "Reserved names are still rejected:\n";
+var_dump(@fopen('\\\\.\\' . $allowed . $sep . 'NUL', 'wb') === false);
+var_dump(file_exists('\\\\?\\' . $allowed . $sep . 'NUL'));
+
+echo "open_basedir sees the same path for all spellings:\n";
+ini_set('open_basedir', $allowed);
+foreach ($spellings as $name => $path) {
+    echo "$name: ";
+    var_dump(@file_get_contents('\\\\.\\' . $allowed . $sep . 'ok.txt') === 'ok');
+    var_dump(@file_get_contents($path) === false);
+    var_dump(@file_get_contents(str_replace($junction, $secret, $path)) === false);
+}
+
+?>
+--CLEAN--
+<?php
+$dir = __DIR__ . DIRECTORY_SEPARATOR . 'dos_device_prefix';
+exec(sprintf('rmdir /S /Q "%s"', $dir));
+?>
+--EXPECT--
+Junction resolves through all spellings:
+plain: bool(true)
+string(6) "secret"
+dot: bool(true)
+string(6) "secret"
+question: bool(true)
+string(6) "secret"
+Prefixed paths without a drive letter are left alone:
+bool(true)
+Reserved names are still rejected:
+bool(true)
+bool(false)
+open_basedir sees the same path for all spellings:
+plain: bool(true)
+bool(true)
+bool(true)
+dot: bool(true)
+bool(true)
+bool(true)
+question: bool(true)
+bool(true)
+bool(true)