diff --git a/contrib/win32/win32compat/ssh-agent/agent-main.c b/contrib/win32/win32compat/ssh-agent/agent-main.c
index 2b001cd00..92da1bf83 100644
--- a/contrib/win32/win32compat/ssh-agent/agent-main.c
+++ b/contrib/win32/win32compat/ssh-agent/agent-main.c
@@ -37,6 +37,9 @@
 
 #pragma warning(push, 3)
 
+/* Pattern-list of allowed PKCS#11/Security key paths */
+char* allowed_providers = NULL;
+
 int remote_add_provider;
 
 int scm_start_service(DWORD, LPWSTR*);
@@ -134,8 +137,25 @@ wmain(int argc, wchar_t **wargv)
 					fatal("Unknown -O option; only allow-remote-pkcs11 is supported");
 				}
 			}
+			else if (wcsncmp(wargv[i], L"-P", 2) == 0) {
+				if (allowed_providers != NULL)
+					fatal("-P option already specified");
+				if ((i + 1) < argc) {
+					i++;
+					if ((allowed_providers = utf16_to_utf8(wargv[i])) == NULL)
+						fatal("Invalid argument for -P option");
+				}
+				else {
+					fatal("Missing argument for -P option");
+				}
+			}
 		}
 	}
+
+	if (allowed_providers == NULL) {
+		agent_initialize_allow_list();
+	}
+
 	if (!StartServiceCtrlDispatcherW(dispatch_table)) {
 		if (GetLastError() == ERROR_FAILED_SERVICE_CONTROLLER_CONNECT) {
 			/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
diff --git a/contrib/win32/win32compat/ssh-agent/agent.c b/contrib/win32/win32compat/ssh-agent/agent.c
index adac352c9..9f3400004 100644
--- a/contrib/win32/win32compat/ssh-agent/agent.c
+++ b/contrib/win32/win32compat/ssh-agent/agent.c
@@ -34,9 +34,11 @@
 #include <UserEnv.h>
 #include "..\misc_internal.h"
 #include <pwd.h>
+#include "xmalloc.h"
 
 #define BUFSIZE 5 * 1024
 
+extern char* allowed_providers;
 extern int remote_add_provider;
 
 char* sshagent_con_username;
@@ -170,11 +172,11 @@ agent_listen_loop()
 				GetModuleFileNameW(NULL, module_path, PATH_MAX);
 				SetHandleInformation(con, HANDLE_FLAG_INHERIT, HANDLE_FLAG_INHERIT);
 				if (remote_add_provider == 1) {
-					if (swprintf_s(path, PATH_MAX, L"%s %d %s", module_path, (int)(intptr_t)con, L"-Oallow-remote-pkcs11") == -1)
+					if (swprintf_s(path, PATH_MAX, L"%s %d %s -P \"%S\"", module_path, (int)(intptr_t)con, L"-Oallow-remote-pkcs11", allowed_providers) == -1)
 						verbose("Failed to create child process %ls ERROR:%d", module_path, GetLastError());
 				}
 				else {
-					if (swprintf_s(path, PATH_MAX, L"%s %d", module_path, (int)(intptr_t)con) == -1)
+					if (swprintf_s(path, PATH_MAX, L"%s %d -P \"%S\"", module_path, (int)(intptr_t)con, allowed_providers) == -1)
 						verbose("Failed to create child process %ls ERROR:%d", module_path, GetLastError());
 				}
 				if (CreateProcessW(NULL, path, NULL, NULL, TRUE, DETACHED_PROCESS, NULL, NULL, &si, &pi) == FALSE) {
@@ -408,3 +410,30 @@ agent_process_connection(HANDLE pipe)
 	iocp_work(NULL);
 }
 
+void 
+agent_initialize_allow_list() {
+	/* 
+	 * allowed paths for PKCS11 libraries,
+	 * initialize to ProgramFiles and ProgramFiles(x86) by default 
+	 * upstream uses /usr/lib/* and /usr/local/lib/* 
+	 */
+	size_t prog_files_len = 0, prog_files_x86_len = 0;
+	char* prog_files = NULL, * prog_files_x86 = NULL;
+
+	_dupenv_s(&prog_files, &prog_files_len, "ProgramFiles");
+	if (!prog_files)
+		fatal("couldn't find ProgramFiles environment variable");
+	convertToForwardslash(prog_files);
+
+	_dupenv_s(&prog_files_x86, &prog_files_x86_len, "ProgramFiles(x86)");
+	if (!prog_files_x86)
+		fatal("couldn't find ProgramFiles environment variable");
+	convertToForwardslash(prog_files_x86);
+
+	size_t allowed_providers_len = 1 + prog_files_len + 4 + prog_files_x86_len + 3;
+	allowed_providers = xmalloc(allowed_providers_len);
+	sprintf_s(allowed_providers, allowed_providers_len, "/%s/*,/%s/*", prog_files, prog_files_x86);
+
+	free(prog_files);
+	free(prog_files_x86);
+}
diff --git a/contrib/win32/win32compat/ssh-agent/agent.h b/contrib/win32/win32compat/ssh-agent/agent.h
index 5313d7e6e..3437d4656 100644
--- a/contrib/win32/win32compat/ssh-agent/agent.h
+++ b/contrib/win32/win32compat/ssh-agent/agent.h
@@ -63,3 +63,4 @@ void agent_start(BOOL);
 void agent_process_connection(HANDLE);
 void agent_shutdown();
 void agent_cleanup_connection(struct agent_connection*);
+void agent_initialize_allow_list();
diff --git a/contrib/win32/win32compat/ssh-agent/keyagent-request.c b/contrib/win32/win32compat/ssh-agent/keyagent-request.c
index 0304f589f..add0bc380 100644
--- a/contrib/win32/win32compat/ssh-agent/keyagent-request.c
+++ b/contrib/win32/win32compat/ssh-agent/keyagent-request.c
@@ -32,6 +32,7 @@
 #include "agent.h"
 #include "agent-request.h"
 #include "config.h"
+#include "match.h"
 #include <sddl.h>
 #ifdef ENABLE_PKCS11
 #include "ssh-pkcs11.h"
@@ -44,6 +45,7 @@
 #define MAX_VALUE_NAME_LENGTH 16383
 #define MAX_VALUE_DATA_LENGTH 2048
 
+extern char* allowed_providers;
 extern int remote_add_provider;
 
 /* 
@@ -675,6 +677,12 @@ int process_add_smartcard_key(struct sshbuf* request, struct sshbuf* response, s
 		goto done;
 	}
 
+	if (match_pattern_list(canonical_provider, allowed_providers, 0) != 1) {
+		verbose("refusing PKCS#11 add of \"%.100s\": "
+			"provider not allowed", canonical_provider);
+		goto done;
+	}
+
 	// Remove 'drive root' if exists
 	if (canonical_provider[0] == '/')
 		memmove(canonical_provider, canonical_provider + 1, strlen(canonical_provider));
@@ -766,6 +774,8 @@ done:
 		free(pubkey_blob);
 	if (provider)
 		free(provider);
+	if (allowed_providers)
+		free(allowed_providers);
 	if (pin) {
 		SecureZeroMemory(pin, (DWORD)pin_len);
 		free(pin);
diff --git a/scp.c b/scp.c
index 7134dfecb..ff0f9b275 100644
--- a/scp.c
+++ b/scp.c
@@ -2117,7 +2117,11 @@ sink(int argc, char **argv, const char *src)
 			SCREWUP("size out of range");
 		size = (off_t)ull;
 
+#ifdef WINDOWS
+		if (*cp == '\0' || strchr(cp, '/') != NULL || strchr(cp, '\\') != NULL ||
+#else
 		if (*cp == '\0' || strchr(cp, '/') != NULL ||
+#endif
 		    strcmp(cp, ".") == 0 || strcmp(cp, "..") == 0) {
 			run_err("error: unexpected filename: %s", cp);
 			exit(1);
diff --git a/sftp-client.c b/sftp-client.c
index 7efbe04b1..9ffcddff6 100644
--- a/sftp-client.c
+++ b/sftp-client.c
@@ -84,7 +84,12 @@ extern int showprogress;
 #ifdef HAVE_CYGWIN
 # define SFTP_DIRECTORY_CHARS      "/\\"
 #else /* HAVE_CYGWIN */
+#ifdef WINDOWS
+// Win32-OpenSSH converts all '/' to '\\' so search for '\\' instead
+# define SFTP_DIRECTORY_CHARS      "\\"
+#else
 # define SFTP_DIRECTORY_CHARS      "/"
+#endif /* WINDOWS */
 #endif /* HAVE_CYGWIN */
 
 struct sftp_conn {