Update.

src/connection.c

@@ -483,28 +483,7 @@ void connection_connect_to_upstream(connection_t *client, const char *data, size
             const char *old_host_header_start = NULL;
             const char *old_host_header_end = NULL;
 
-        const char *current = data;
+            if (http_find_header_line_bounds(data, data_len, "Host", &old_host_header_start, &old_host_header_end)) {
-        const char *end = data + data_len;
-        while(current < end) {
-            const char* line_end = memchr(current, '\n', end - current);
-            if (!line_end) break;
-
-            if (strncasecmp(current, "Host", 4) == 0) {
-                const char *colon = current + 4;
-                while (colon < line_end && (*colon == ' ' || *colon == '\t')) {
-                    colon++;
-                }
-                if (colon < line_end && *colon == ':') {
-                    old_host_header_start = current;
-                    old_host_header_end = line_end + 1;
-                    break;
-                }
-            }
-
-            current = line_end + 1;
-        }
-
-        if (old_host_header_start) {
                 int is_default_port = (route->use_ssl && route->upstream_port == 443) ||
                                       (!route->use_ssl && route->upstream_port == 80);
                 if (is_default_port) {

src/http.c

@@ -251,3 +251,35 @@ int http_rewrite_content_length(char *headers, size_t *headers_len, size_t max_l
     *headers_len = new_total_len;
     return 1;
 }
+
+int http_find_header_line_bounds(const char* data, size_t len, const char* name, const char** line_start, const char** line_end) {
+    size_t name_len = strlen(name);
+    const char* end = data + len;
+
+    for (const char* p = data; p < end; ) {
+        const char* current_line_end = memchr(p, '\n', end - p);
+        if (!current_line_end) break;
+
+        const char* line_actual_end = current_line_end;
+        if (line_actual_end > p && *(line_actual_end - 1) == '\r') {
+            line_actual_end--;
+        }
+
+        // Check for header name followed by optional whitespace and a colon
+        if ((size_t)(line_actual_end - p) > name_len && strncasecmp(p, name, name_len) == 0) {
+            const char* colon_pos = p + name_len;
+            while (colon_pos < line_actual_end && (*colon_pos == ' ' || *colon_pos == '\t')) {
+                colon_pos++;
+            }
+            if (colon_pos < line_actual_end && *colon_pos == ':') {
+                *line_start = p;
+                *line_end = current_line_end + 1; // Include the \n (and \r if present)
+                return 1;
+            }
+        }
+        p = current_line_end + 1;
+    }
+    *line_start = NULL;
+    *line_end = NULL;
+    return 0;
+}

src/http.h

@@ -11,5 +11,6 @@ int http_detect_binary_content(const char *data, size_t len);
 long http_get_content_length(const char *headers, size_t headers_len);
 int http_find_headers_end(const char *data, size_t len, size_t *headers_end);
 int http_rewrite_content_length(char *headers, size_t *headers_len, size_t max_len, long new_length);
+int http_find_header_line_bounds(const char* data, size_t len, const char* name, const char** line_start, const char** line_end);
 
 #endif