diff --git a/CHANGES b/CHANGES
index 89e7d07..ada0ea0 100644
--- a/CHANGES
+++ b/CHANGES
@@ -25,7 +25,9 @@ corrections:
  
 	On big endian platforms with type long >32bit the range option applied a
 	bad base address. Thanks to hejia hejia for reporting and fixing this bug.
- 
+
+	Red Hat issue 1022063: out-of-range shifts on net mask bits
+
 	Red Hat issue 1022062: strcpy misuse in xiosetsockaddrenv_ip4()
 
 	Red Hat issue 1022048: strncpy hardening: corrected suspicious strncpy()
diff --git a/test.sh b/test.sh
index fc0db38..860ea9a 100755
--- a/test.sh
+++ b/test.sh
@@ -11673,6 +11673,55 @@ PORT=$((PORT+1))
 N=$((N+1))
 
 
+# socat up to version 1.7.2.3
+# had a bug that converted a bit mask of 0 internally to 0xffffffff
+NAME=TCP4RANGE_0BITS
+case "$TESTS" in
+*%functions%*|*%tcp%*|*%tcp4%*|*%ip4%*|*%range%*|*%$NAME%*)
+TEST="$NAME: correct evaluation of range mask 0"
+if ! eval $NUMCOND; then :;
+elif [ -z "$SECONDADDR" ]; then
+    # we need access to a second addresses
+    $PRINTF "test $F_n $TEST... ${YELLOW}need a second IPv4 address${NORMAL}\n" $N
+    numCANT=$((numCANT+1))
+else
+tf="$td/test$N.stdout"
+tdiff="$td/test$N.diff"
+da="test$N $(date) $RANDOM"
+#testserversec "$N" "$TEST" "$opts -s" "tcp4-l:$PORT,reuseaddr,fork,retry=1" "" "range=$SECONDADDR/32" "tcp4:127.0.0.1:$PORT" 4 tcp $PORT 0
+CMD0="$SOCAT $opts TCP4-LISTEN:$PORT,reuseaddr,range=127.0.0.1/0 CREATE:$tf"
+CMD1="$SOCAT $opts - TCP4-CONNECT:$SECONDADDR:$PORT,bind=$SECONDADDR"
+printf "test $F_n $TEST... " $N
+$CMD0 2>"${te}0" &
+pid0=$!
+waittcp4port $PORT 1
+echo "$da" |$CMD1 >"${tf}1" 2>"${te}1"
+rc1=$?
+kill $pid0 2>/dev/null; wait
+if [ $rc1 != 0 ]; then
+    $PRINTF "${YELLOW}invocation failed${NORMAL}\n"
+    numCANT=$((numCANT+1))
+elif ! [ -f "$tf" ]; then
+    $PRINTF "$FAILED\n"
+    echo "$CMD0 &"
+    echo "$CMD1"
+    cat "${te}0"
+    cat "${te}1"
+    numFAIL=$((numFAIL+1))
+elif ! echo "$da" |diff - "$tf" >"$tdiff"; then
+    $PRINTF "${YELLOW}diff failed${NORMAL}\n"
+    numCANT=$((numCANT+1))
+else
+    $PRINTF "$OK\n"
+    numOK=$((numOK+1))
+fi
+
+fi ;; # $SECONDADDR, NUMCOND
+esac
+PORT=$((PORT+1))
+N=$((N+1))
+
+
 ###############################################################################
 # here come tests that might affect your systems integrity. Put normal tests
 # before this paragraph.
diff --git a/xio-ip4.c b/xio-ip4.c
index 0e41d3f..dacbade 100644
--- a/xio-ip4.c
+++ b/xio-ip4.c
@@ -20,7 +20,7 @@ int xioparsenetwork_ip4(const char *rangename, struct xiorange *range) {
    struct in_addr *netmask_in = &range->netmask.ip4.sin_addr;
    char *rangename1;	/* a copy of rangename with writing allowed */
    char *delimpos;	/* absolute address of delimiter */
-   int bits;
+   unsigned int bits;	/* netmask bits */
 
    if ((rangename1 = strdup(rangename)) == NULL) {
       Error1("strdup(\"%s\"): out of memory", rangename);
@@ -28,8 +28,20 @@ int xioparsenetwork_ip4(const char *rangename, struct xiorange *range) {
    }
 
    if (delimpos = strchr(rangename1, '/')) {
-      bits = strtoul(delimpos+1, NULL, 10);
-      netmask_in->s_addr = htonl((0xffffffff << (32-bits)));
+      char *endptr;
+      bits = strtoul(delimpos+1, &endptr, 10);
+      if (! ((*(delimpos+1) != '\0') && (*endptr == '\0'))) {
+	 Error1("not a valid netmask in \"%s\"", rangename);
+	 bits = 32;     /* most secure selection */
+      } else if (bits > 32) {
+	 Error1("netmask \"%s\" is too large", rangename);
+	 bits = 32;
+      }
+      if (bits <= 0) {
+	 netmask_in->s_addr = 0;
+      } else {
+	 netmask_in->s_addr = htonl((0xffffffff << (32-bits)));
+      }
    } else if (delimpos = strchr(rangename1, ':')) {
       if ((maskaddr = Gethostbyname(delimpos+1)) == NULL) {
 	 /* note: cast is req on AIX: */
diff --git a/xio-ip6.c b/xio-ip6.c
index 2644c00..6fd5507 100644
--- a/xio-ip6.c
+++ b/xio-ip6.c
@@ -78,7 +78,8 @@ const struct optdesc opt_ipv6_recvpathmtu = { "ipv6-recvpathmtu", "recvpathmtu",
 int xioparsenetwork_ip6(const char *rangename, struct xiorange *range) {
    char *delimpos;	/* absolute address of delimiter */
    size_t delimind;	/* index of delimiter in string */
-   int bits;
+   unsigned int bits;
+   char *endptr;
    char *baseaddr;
    union sockaddr_union sockaddr;
    socklen_t sockaddrlen = sizeof(sockaddr);
@@ -112,22 +113,32 @@ int xioparsenetwork_ip6(const char *rangename, struct xiorange *range) {
    rangeaddr->u6_addr32[1] = nameaddr->u6_addr32[1];
    rangeaddr->u6_addr32[2] = nameaddr->u6_addr32[2];
    rangeaddr->u6_addr32[3] = nameaddr->u6_addr32[3];
-   bits = strtoul(delimpos+1, NULL, 10);
-   if (bits > 128) {
-      Error1("invalid number of mask bits %u", bits);
-      return STAT_NORETRY;
+   bits = strtoul(delimpos+1, &endptr, 10);
+   if (! ((*(delimpos+1) != '\0') && (*endptr == '\0'))) {
+      Error1("not a valid netmask in \"%s\"", rangename);
+      bits = 128;      /* most secure selection */
+   } else if (bits > 128) {
+      Error1("netmask \"%s\" is too large", rangename);
+      bits = 128;
    }
-   if (bits < 32) {
+
+   /* I am starting to dislike C...uint32_t << 32 is undefined... */
+   if (bits == 0) {
+      rangemask->u6_addr32[0] = 0;
+      rangemask->u6_addr32[1] = 0;
+      rangemask->u6_addr32[2] = 0;
+      rangemask->u6_addr32[3] = 0;
+   } else if (bits <= 32) {
       rangemask->u6_addr32[0] = htonl(0xffffffff << (32-bits));
       rangemask->u6_addr32[1] = 0;
       rangemask->u6_addr32[2] = 0;
       rangemask->u6_addr32[3] = 0;
-   } else if (bits < 64) {
+   } else if (bits <= 64) {
       rangemask->u6_addr32[0] = 0xffffffff;
       rangemask->u6_addr32[1] = htonl(0xffffffff << (64-bits));
       rangemask->u6_addr32[2] = 0;
       rangemask->u6_addr32[3] = 0;
-   } else if (bits < 96) {
+   } else if (bits <= 96) {
       rangemask->u6_addr32[0] = 0xffffffff;
       rangemask->u6_addr32[1] = 0xffffffff;
       rangemask->u6_addr32[2] = htonl(0xffffffff << (96-bits));