diff --git a/src/openvpn/argv.c b/src/openvpn/argv.c
index 9100a196..9606f382 100644
--- a/src/openvpn/argv.c
+++ b/src/openvpn/argv.c
@@ -131,64 +131,6 @@ argv_insert_head(const struct argv *a, const char *head)
     return r;
 }
 
-static char *
-argv_term(const char **f)
-{
-    const char *p = *f;
-    const char *term = NULL;
-    size_t termlen = 0;
-
-    if (*p == '\0')
-    {
-        return NULL;
-    }
-
-    while (true)
-    {
-        const int c = *p;
-        if (c == '\0')
-        {
-            break;
-        }
-        if (term)
-        {
-            if (!isspace(c))
-            {
-                ++termlen;
-            }
-            else
-            {
-                break;
-            }
-        }
-        else
-        {
-            if (!isspace(c))
-            {
-                term = p;
-                termlen = 1;
-            }
-        }
-        ++p;
-    }
-    *f = p;
-
-    if (term)
-    {
-        char *ret;
-        ASSERT(termlen > 0);
-        ret = malloc(termlen + 1);
-        check_malloc_return(ret);
-        memcpy(ret, term, termlen);
-        ret[termlen] = '\0';
-        return ret;
-    }
-    else
-    {
-        return NULL;
-    }
-}
-
 const char *
 argv_str(const struct argv *a, struct gc_arena *gc, const unsigned int flags)
 {
@@ -218,119 +160,151 @@ argv_msg_prefix(const int msglev, const struct argv *a, const char *prefix)
     gc_free(&gc);
 }
 
-static void
+
+/*
+ * argv_prep_format - prepare argv format string for further processing
+ *
+ * Individual argument must be separated by space. Ignores leading and trailing spaces.
+ * Consecutive spaces count as one. Returns prepared format string, with space replaced
+ * by delim and adds the number of arguments to the count parameter.
+ */
+static char *
+argv_prep_format(const char *format, const char delim, size_t *count, struct gc_arena *gc)
+{
+    int i, j;
+    char *f;
+    bool in_token = false;
+
+    if (format == NULL)
+    {
+        return NULL;
+    }
+
+    f = gc_malloc(strlen(format) + 1, true, gc);
+    for (i = 0, j = 0; i < strlen(format); i++)
+    {
+        if (format[i] == ' ')
+        {
+            in_token = false;
+            continue;
+        }
+
+        if (!in_token)
+        {
+            ++*count;
+
+            /*
+             * We don't add any delimiter to the resulting
+             * format string before something has been added there.
+             * The resulting format string will never start with a delimiter.
+             */
+            if (j > 0)
+            {
+                f[j++] = delim;
+            }
+        }
+
+        f[j++] = format[i];
+        in_token = true;
+    }
+
+    return f;
+}
+
+/*
+ * argv_printf_arglist - create a struct argv from a format string
+ *
+ * Instead of parsing the format string ourselves place delimiters via argv_prep_format()
+ * before we let libc's printf() do the parsing. Then split the resulting string at the
+ * injected delimiters.
+ */
+static bool
 argv_printf_arglist(struct argv *a, const char *format, va_list arglist)
 {
-    char *term;
-    const char *f = format;
+    struct gc_arena gc = gc_new();
+    const char delim = 0x1D;  /* ASCII Group Separator (GS) */
+    char *f, *buf, *end;
+    size_t argc, size;
+    bool res = false;
+    va_list tmplist;
+    int len;
 
     argv_extend(a, 1); /* ensure trailing NULL */
 
-    while ((term = argv_term(&f)) != NULL)
+    argc = a->argc;
+    f = argv_prep_format(format, delim, &argc, &gc);
+    if (f == NULL)
     {
-        if (term[0] == '%')
-        {
-            if (!strcmp(term, "%s"))
-            {
-                char *s = va_arg(arglist, char *);
-                if (!s)
-                {
-                    s = "";
-                }
-                argv_append(a, string_alloc(s, NULL));
-            }
-            else if (!strcmp(term, "%d"))
-            {
-                char numstr[64];
-                openvpn_snprintf(numstr, sizeof(numstr), "%d", va_arg(arglist, int));
-                argv_append(a, string_alloc(numstr, NULL));
-            }
-            else if (!strcmp(term, "%u"))
-            {
-                char numstr[64];
-                openvpn_snprintf(numstr, sizeof(numstr), "%u", va_arg(arglist, unsigned int));
-                argv_append(a, string_alloc(numstr, NULL));
-            }
-            else if (!strcmp(term, "%lu"))
-            {
-                char numstr[64];
-                openvpn_snprintf(numstr, sizeof(numstr), "%lu",
-                                 va_arg(arglist, unsigned long));
-                argv_append(a, string_alloc(numstr, NULL));
-            }
-            else if (!strcmp(term, "%s/%d"))
-            {
-                char numstr[64];
-                char *s = va_arg(arglist, char *);
-
-                if (!s)
-                {
-                    s = "";
-                }
+        goto out;
+    }
 
-                openvpn_snprintf(numstr, sizeof(numstr), "%d", va_arg(arglist, int));
+    /* determine minimum buffer size */
+    va_copy(tmplist, arglist);
+    len = vsnprintf(NULL, 0, f, tmplist);
+    va_end(tmplist);
+    if (len < 0)
+    {
+        goto out;
+    }
 
-                {
-                    const size_t len = strlen(s) + strlen(numstr) + 2;
-                    char *combined = (char *) malloc(len);
-                    check_malloc_return(combined);
+    size = adjust_power_of_2(len + 1);
+    buf = gc_malloc(size, false, &gc);
+    len = vsnprintf(buf, size, f, arglist);
+    if (len < 0 || len >= size)
+    {
+        goto out;
+    }
 
-                    strcpy(combined, s);
-                    strcat(combined, "/");
-                    strcat(combined, numstr);
-                    argv_append(a, combined);
-                }
-            }
-            else if (!strcmp(term, "%s%sc"))
-            {
-                char *s1 = va_arg(arglist, char *);
-                char *s2 = va_arg(arglist, char *);
-                char *combined;
+    /* split the string at the delimiters */
+    end = strchr(buf, delim);
+    while (end)
+    {
+        *end = '\0';
+        argv_append(a, string_alloc(buf, NULL));
+        buf = end + 1;
+        end = strchr(buf, delim);
+    }
+    argv_append(a, string_alloc(buf, NULL));
 
-                if (!s1)
-                {
-                    s1 = "";
-                }
-                if (!s2)
-                {
-                    s2 = "";
-                }
-                combined = (char *) malloc(strlen(s1) + strlen(s2) + 1);
-                check_malloc_return(combined);
-                strcpy(combined, s1);
-                strcat(combined, s2);
-                argv_append(a, combined);
-            }
-            else
-            {
-                ASSERT(0);
-            }
-            free(term);
-        }
-        else
-        {
-            argv_append(a, term);
-        }
+    if (a->argc != argc)
+    {
+        /* Someone snuck in a GS (0x1D), fail gracefully */
+        argv_reset(a);
+        argv_extend(a, 1); /* ensure trailing NULL */
+        goto out;
     }
+
+    res = true;
+
+out:
+    gc_free(&gc);
+    return res;
 }
 
-void
+
+
+bool
 argv_printf(struct argv *a, const char *format, ...)
 {
+    bool res;
     va_list arglist;
-    argv_reset(a);
+
     va_start(arglist, format);
-    argv_printf_arglist(a, format, arglist);
+    argv_reset(a);
+    res = argv_printf_arglist(a, format, arglist);
     va_end(arglist);
+    return res;
 }
 
-void
+bool
 argv_printf_cat(struct argv *a, const char *format, ...)
 {
+    bool res;
     va_list arglist;
     va_start(arglist, format);
-    argv_printf_arglist(a, format, arglist);
+    res = argv_printf_arglist(a, format, arglist);
     va_end(arglist);
+    return res;
 }
 
 void
diff --git a/src/openvpn/argv.h b/src/openvpn/argv.h
index 9d9f3873..b9105a43 100644
--- a/src/openvpn/argv.h
+++ b/src/openvpn/argv.h
@@ -52,7 +52,7 @@ void argv_msg_prefix(const int msglev, const struct argv *a, const char *prefix)
 
 void argv_parse_cmd(struct argv *a, const char *s);
 
-void argv_printf(struct argv *a, const char *format, ...)
+bool argv_printf(struct argv *a, const char *format, ...)
 #ifdef __GNUC__
 #if __USE_MINGW_ANSI_STDIO
 __attribute__ ((format(gnu_printf, 2, 3)))
@@ -62,7 +62,7 @@ __attribute__ ((format(__printf__, 2, 3)))
 #endif
 ;
 
-void argv_printf_cat(struct argv *a, const char *format, ...)
+bool argv_printf_cat(struct argv *a, const char *format, ...)
 #ifdef __GNUC__
 #if __USE_MINGW_ANSI_STDIO
 __attribute__ ((format(gnu_printf, 2, 3)))
diff --git a/src/openvpn/route.c b/src/openvpn/route.c
index d97e8dba..9649d197 100644
--- a/src/openvpn/route.c
+++ b/src/openvpn/route.c
@@ -1614,7 +1614,7 @@ add_route(struct route_ipv4 *r,
 #elif defined (_WIN32)
     {
         DWORD ai = TUN_ADAPTER_INDEX_INVALID;
-        argv_printf(&argv, "%s%sc ADD %s MASK %s %s",
+        argv_printf(&argv, "%s%s ADD %s MASK %s %s",
                     get_win_sys_path(),
                     WIN_ROUTE_PATH_SUFFIX,
                     network,
@@ -1979,7 +1979,7 @@ add_route_ipv6(struct route_ipv6 *r6, const struct tuntap *tt, unsigned int flag
         device = buf_bptr(&out);
 
         /* netsh interface ipv6 add route 2001:db8::/32 MyTunDevice */
-        argv_printf(&argv, "%s%sc interface ipv6 add route %s/%d %s",
+        argv_printf(&argv, "%s%s interface ipv6 add route %s/%d %s",
                     get_win_sys_path(),
                     NETSH_PATH_SUFFIX,
                     network,
@@ -2186,7 +2186,7 @@ delete_route(struct route_ipv4 *r,
 
 #elif defined (_WIN32)
 
-    argv_printf(&argv, "%s%sc DELETE %s MASK %s %s",
+    argv_printf(&argv, "%s%s DELETE %s MASK %s %s",
                 get_win_sys_path(),
                 WIN_ROUTE_PATH_SUFFIX,
                 network,
@@ -2426,7 +2426,7 @@ delete_route_ipv6(const struct route_ipv6 *r6, const struct tuntap *tt, unsigned
         device = buf_bptr(&out);
 
         /* netsh interface ipv6 delete route 2001:db8::/32 MyTunDevice */
-        argv_printf(&argv, "%s%sc interface ipv6 delete route %s/%d %s",
+        argv_printf(&argv, "%s%s interface ipv6 delete route %s/%d %s",
                     get_win_sys_path(),
                     NETSH_PATH_SUFFIX,
                     network,
diff --git a/src/openvpn/tun.c b/src/openvpn/tun.c
index 948fd17d..f80aedf8 100644
--- a/src/openvpn/tun.c
+++ b/src/openvpn/tun.c
@@ -994,7 +994,7 @@ do_ifconfig_ipv6(struct tuntap *tt, const char *ifname, int tun_mtu,
 
         openvpn_snprintf(iface, sizeof(iface), "interface=%lu",
                          tt->adapter_index);
-        argv_printf(&argv, "%s%sc interface ipv6 set address %s %s store=active",
+        argv_printf(&argv, "%s%s interface ipv6 set address %s %s store=active",
                     get_win_sys_path(), NETSH_PATH_SUFFIX, iface,
                     ifconfig_ipv6_local);
         netsh_command(&argv, 4, M_FATAL);
@@ -4873,14 +4873,14 @@ ipconfig_register_dns(const struct env_set *es)
     msg(D_TUNTAP_INFO, "Start ipconfig commands for register-dns...");
     netcmd_semaphore_lock();
 
-    argv_printf(&argv, "%s%sc /flushdns",
+    argv_printf(&argv, "%s%s /flushdns",
                 get_win_sys_path(),
                 WIN_IPCONFIG_PATH_SUFFIX);
     argv_msg(D_TUNTAP_INFO, &argv);
     status = openvpn_execve_check(&argv, es, 0, err);
     argv_reset(&argv);
 
-    argv_printf(&argv, "%s%sc /registerdns",
+    argv_printf(&argv, "%s%s /registerdns",
                 get_win_sys_path(),
                 WIN_IPCONFIG_PATH_SUFFIX);
     argv_msg(D_TUNTAP_INFO, &argv);
@@ -4994,8 +4994,8 @@ netsh_set_dns6_servers(const struct in6_addr *addr_list,
     for (int i = 0; i < addr_len; ++i)
     {
         const char *fmt = (i == 0) ?
-                          "%s%sc interface ipv6 set dns %s static %s"
-                          : "%s%sc interface ipv6 add dns %s %s";
+                          "%s%s interface ipv6 set dns %s static %s"
+                          : "%s%s interface ipv6 add dns %s %s";
         argv_printf(&argv, fmt, get_win_sys_path(),
                     NETSH_PATH_SUFFIX, flex_name,
                     print_in6_addr(addr_list[i], 0, &gc));
@@ -5042,7 +5042,7 @@ netsh_ifconfig_options(const char *type,
     /* delete existing DNS/WINS settings from TAP interface */
     if (delete_first)
     {
-        argv_printf(&argv, "%s%sc interface ip delete %s %s all",
+        argv_printf(&argv, "%s%s interface ip delete %s %s all",
                     get_win_sys_path(),
                     NETSH_PATH_SUFFIX,
                     type,
@@ -5059,8 +5059,8 @@ netsh_ifconfig_options(const char *type,
             if (delete_first || !test_first || !ip_addr_member_of(addr_list[i], current))
             {
                 const char *fmt = count ?
-                                  "%s%sc interface ip add %s %s %s"
-                                  : "%s%sc interface ip set %s %s static %s";
+                                  "%s%s interface ip add %s %s %s"
+                                  : "%s%s interface ip set %s %s static %s";
 
                 argv_printf(&argv, fmt,
                             get_win_sys_path(),
@@ -5136,7 +5136,7 @@ netsh_ifconfig(const struct tuntap_options *to,
         else
         {
             /* example: netsh interface ip set address my-tap static 10.3.0.1 255.255.255.0 */
-            argv_printf(&argv, "%s%sc interface ip set address %s static %s %s",
+            argv_printf(&argv, "%s%s interface ip set address %s static %s %s",
                         get_win_sys_path(),
                         NETSH_PATH_SUFFIX,
                         flex_name,
@@ -5185,7 +5185,7 @@ netsh_enable_dhcp(const struct tuntap_options *to,
 
     /* example: netsh interface ip set address my-tap dhcp */
     argv_printf(&argv,
-                "%s%sc interface ip set address %s dhcp",
+                "%s%s interface ip set address %s dhcp",
                 get_win_sys_path(),
                 NETSH_PATH_SUFFIX,
                 actual_name);
@@ -6100,7 +6100,7 @@ close_tun(struct tuntap *tt)
             /* netsh interface ipv6 delete address \"%s\" %s */
             ifconfig_ipv6_local = print_in6_addr(tt->local_ipv6, 0,  &gc);
             argv_printf(&argv,
-                        "%s%sc interface ipv6 delete address %s %s store=active",
+                        "%s%s interface ipv6 delete address %s %s store=active",
                         get_win_sys_path(),
                         NETSH_PATH_SUFFIX,
                         tt->actual_name,
@@ -6112,7 +6112,7 @@ close_tun(struct tuntap *tt)
             if (tt->options.dns6_len > 0)
             {
                 argv_printf(&argv,
-                            "%s%sc interface ipv6 delete dns %s all",
+                            "%s%s interface ipv6 delete dns %s all",
                             get_win_sys_path(),
                             NETSH_PATH_SUFFIX,
                             tt->actual_name);
diff --git a/tests/unit_tests/openvpn/test_argv.c b/tests/unit_tests/openvpn/test_argv.c
index 0fdd3f0a..9b67fade 100644
--- a/tests/unit_tests/openvpn/test_argv.c
+++ b/tests/unit_tests/openvpn/test_argv.c
@@ -9,6 +9,7 @@
 #include <setjmp.h>
 #include <cmocka.h>
 #include <assert.h>
+#include <stdbool.h>
 
 #include "argv.h"
 #include "buffer.h"
@@ -53,23 +54,69 @@ argv_printf_cat__multiple_spaces_in_format__parsed_as_one(void **state)
     argv_reset(&a);
 }
 
+static void
+argv_printf__embedded_format_directive__replaced_in_output(void **state)
+{
+    struct argv a = argv_new();
+
+    argv_printf(&a, "<p1:%s>", PATH1);
+    assert_int_equal(a.argc, 1);
+    assert_string_equal(a.argv[0], "<p1:" PATH1 ">");
+
+    argv_reset(&a);
+}
+
+static void
+argv_printf__group_sep_in_arg__fail_no_ouput(void **state)
+{
+    struct argv a = argv_new();
+
+    assert_false(argv_printf(&a, "tool --do %s", "this\035--harmful"));
+    assert_int_equal(a.argc, 0);
+
+    argv_reset(&a);
+}
+
 static void
 argv_printf__combined_path_with_spaces__argc_correct(void **state)
 {
     struct argv a = argv_new();
 
-    argv_printf(&a, "%s%sc", PATH1, PATH2);
+    argv_printf(&a, "%s%s", PATH1, PATH2);
     assert_int_equal(a.argc, 1);
 
-    argv_printf(&a, "%s%sc %d", PATH1, PATH2, 42);
+    argv_printf(&a, "%s%s %d", PATH1, PATH2, 42);
     assert_int_equal(a.argc, 2);
 
-    argv_printf(&a, "foo %s%sc %s x y", PATH2, PATH1, "foo");
+    argv_printf(&a, "foo %s%s %s x y", PATH2, PATH1, "foo");
     assert_int_equal(a.argc, 5);
 
     argv_reset(&a);
 }
 
+static void
+argv_printf__empty_parameter__argc_correct(void **state)
+{
+    struct argv a = argv_new();
+
+    argv_printf(&a, "%s", "");
+    assert_int_equal(a.argc, 1);
+
+    argv_printf(&a, "%s %s", PATH1, "");
+    assert_int_equal(a.argc, 2);
+
+    argv_printf(&a, "%s %s %s", PATH1, "", PARAM1);
+    assert_int_equal(a.argc, 3);
+
+    argv_printf(&a, "%s %s %s %s", PATH1, "", "", PARAM1);
+    assert_int_equal(a.argc, 4);
+
+    argv_printf(&a, "%s %s", "", PARAM1);
+    assert_int_equal(a.argc, 2);
+
+    argv_free(&a);
+}
+
 static void
 argv_parse_cmd__command_string__argc_correct(void **state)
 {
@@ -113,7 +160,7 @@ argv_str__multiple_argv__correct_output(void **state)
     struct gc_arena gc = gc_new();
     const char *output;
 
-    argv_printf(&a, "%s%sc", PATH1, PATH2);
+    argv_printf(&a, "%s%s", PATH1, PATH2);
     argv_printf_cat(&a, "%s", PARAM1);
     argv_printf_cat(&a, "%s", PARAM2);
     argv_printf_cat(&a, "%d", -1);
@@ -172,7 +219,10 @@ main(void)
     const struct CMUnitTest tests[] = {
         cmocka_unit_test(argv_printf__multiple_spaces_in_format__parsed_as_one),
         cmocka_unit_test(argv_printf_cat__multiple_spaces_in_format__parsed_as_one),
+        cmocka_unit_test(argv_printf__embedded_format_directive__replaced_in_output),
+        cmocka_unit_test(argv_printf__group_sep_in_arg__fail_no_ouput),
         cmocka_unit_test(argv_printf__combined_path_with_spaces__argc_correct),
+        cmocka_unit_test(argv_printf__empty_parameter__argc_correct),
         cmocka_unit_test(argv_parse_cmd__command_string__argc_correct),
         cmocka_unit_test(argv_parse_cmd__command_and_extra_options__argc_correct),
         cmocka_unit_test(argv_printf_cat__used_twice__argc_correct),
