diff '--color=auto' -Naurd privoxy-3.0.28-stable.orig/gateway.c privoxy-3.0.28-stable/gateway.c
--- privoxy-3.0.28-stable.orig/gateway.c	2018-12-30 21:40:13.000000000 +0300
+++ privoxy-3.0.28-stable/gateway.c	2020-07-11 14:55:15.442676106 +0300
@@ -1103,7 +1103,8 @@
    cbuf[client_pos++] = (char)(hostlen & 0xffu);
    assert(sizeof(cbuf) - client_pos > (size_t)255);
    /* Using strncpy because we really want the nul byte padding. */
-   strncpy(cbuf + client_pos, target_host, sizeof(cbuf) - client_pos);
+   strncpy(cbuf + client_pos, target_host, sizeof(cbuf) - client_pos - 1);
+   cbuf[sizeof(cbuf)-1] = 0;
    client_pos += (hostlen & 0xffu);
    cbuf[client_pos++] = (char)((target_port >> 8) & 0xff);
    cbuf[client_pos++] = (char)((target_port     ) & 0xff);