diff --git a/src/config_parser.c b/src/config_parser.c
index 14b2ed60..bb25f844 100644
--- a/src/config_parser.c
+++ b/src/config_parser.c
@@ -10,6 +10,8 @@
 #include <ctype.h>
 #include "../lib/platform_compat.h"
 #include <errno.h>
+#include <limits.h>
+#include "transport_layer/etcp_connections.h"
 #ifndef _WIN32
 #include <netdb.h>
 #include <ifaddrs.h>
@@ -379,7 +381,15 @@ static int parse_global(const char *key, const char *value, struct global_config
         return 0;
     }
     if (strcmp(key, "bbr_max_cwnd") == 0) {
-        global->bbr_max_cwnd = atoi(value);
+        char* end;
+        errno = 0;
+        long parsed = strtol(value, &end, 10);
+        if (errno || end == value || *end || parsed < INFLIGHT_LIM_MIN || parsed > INT_MAX) {
+            DEBUG_ERROR(DEBUG_CATEGORY_CONFIG, "%s:%d: invalid bbr_max_cwnd '%s'; expected %u..%d bytes",
+                filename, line_num, value, INFLIGHT_LIM_MIN, INT_MAX);
+            return -1;
+        }
+        global->bbr_max_cwnd = (int)parsed;
         return 0;
     }
     if (strcmp(key, "auto_sockets") == 0) {
@@ -1121,7 +1131,12 @@ struct utun_config* parse_config_from_buf(const char *buf, size_t len, const cha
             continue;
         }
         switch (cur_section) {
-            case SECTION_GLOBAL: parse_global(key, value, &cfg->global, filename, line_num); break;
+            case SECTION_GLOBAL:
+                if (parse_global(key, value, &cfg->global, filename, line_num) < 0) {
+                    DEBUG_ERROR(DEBUG_CATEGORY_CONFIG, "%s:%d: invalid global option %s=%s", filename, line_num, key, value);
+                    goto error;
+                }
+                break;
             case SECTION_SERVER: if (cur_server) parse_server(key, value, cur_server, filename, line_num); break;
             case SECTION_CLIENT: if (cur_client) parse_client(key, value, cur_client, cfg->servers, filename, line_num); break;
             case SECTION_ROUTING: if (strcmp(key, "route_subnet") == 0) add_route_entry(&cfg->route_subnets, value); else if (strcmp(key, "my_subnet") == 0) add_route_entry(&cfg->my_subnets, value); else DEBUG_ERROR(DEBUG_CATEGORY_CONFIG, "%s:%d: Unknown routing option '%s'", filename, line_num, key); break;
diff --git a/src/transport_layer/etcp.c b/src/transport_layer/etcp.c
index 26dde4cd..f692929a 100644
--- a/src/transport_layer/etcp.c
+++ b/src/transport_layer/etcp.c
@@ -291,6 +291,11 @@ struct ETCP_CONN* etcp_connection_create(struct UTUN_INSTANCE* instance, char* n
     etcp->inflight_pool = memory_pool_init(sizeof(struct INFLIGHT_PACKET), "inflight_pool");
     etcp->io_pool = memory_pool_init(sizeof(struct ETCP_FRAGMENT), "io_pool");
     etcp->max_inflight = (uint32_t)instance->config->global.bbr_max_cwnd;
+    if (instance->config->global.bbr_max_cwnd < INFLIGHT_LIM_MIN) {
+        DEBUG_WARN(DEBUG_CATEGORY_ETCP, "ETCP config cwnd=%d raised to minimum %u bytes",
+            instance->config->global.bbr_max_cwnd, INFLIGHT_LIM_MIN);
+        etcp->max_inflight = INFLIGHT_LIM_MIN;
+    }
     etcp->optimal_inflight=100000;
     etcp->initialized=0;
     etcp->links_up=0;
@@ -950,9 +955,9 @@ static void input_queue_try_resume(struct ETCP_CONN* etcp) {// при ACK
 // Recalculates connection-level optimal_inflight and resumes input_queue if room opened up.
 void etcp_conn_on_inflight_lim_changed(struct ETCP_CONN* etcp) {
     if (!etcp || etcp->state == 2) return;
-    uint32_t sum = 0;
+    uint64_t sum = 0;
     for (struct ETCP_LINK* tl = etcp->links; tl; tl = tl->next) sum += tl->inflight_lim_bytes;
-    etcp->optimal_inflight = sum;
+    etcp->optimal_inflight = sum > UINT32_MAX ? UINT32_MAX : (uint32_t)sum;
     etcp_conn_wake_sender(etcp);
 }