diff --git a/CHANGES b/CHANGES
index 210d726..93af46b 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,4 +1,17 @@
 
+####################### V 2.0.0-b5:
+
+security:
+	fixed a possible heap buffer overflow in the readline address. This bug
+	could be exploited when all of the following conditions were met:
+	1) one of the addresses is READLINE without the noprompt and without the
+	prompt options.
+	2) the other (almost arbitrary address) reads malicious data (which is
+	then transferred by socat to READLINE).
+	Workaround: when using the READLINE address apply option prompt or
+	noprompt.
+	Full credits to Johan Thillemann for finding and reporting this issue.
+
 ####################### V 2.0.0-b4:
 
 security:
diff --git a/VERSION b/VERSION
index 933d0bd..713ed4f 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-"2.0.0-b4"
+"2.0.0-b5"
diff --git a/test.sh b/test.sh
index 880de5a..7f03573 100755
--- a/test.sh
+++ b/test.sh
@@ -1,6 +1,6 @@
 #! /bin/bash
 # source: test.sh
-# Copyright Gerhard Rieger 2001-2009
+# Copyright Gerhard Rieger 2001-2012
 # Published under the GNU General Public License V.2, see file COPYING
 
 # perform lots of tests on socat
@@ -10528,7 +10528,7 @@ te="$td/test$N.stderr"
 tdiff="$td/test$N.diff"
 da="test$N $(date) $RANDOM"
 # prepare long data - perl might not be installed
-rm -f "$td/terst$N.dat"
+rm -f "$td/test$N.dat"
 i=0; while [ $i -lt 64 ]; do  echo -n "AAAAAAAAAAAAAAAA" >>"$td/test$N.dat"; i=$((i+1)); done
 CMD0="$SOCAT $opts TCP-CONNECT:$(cat "$td/test$N.dat"):$PORT STDIO"
 printf "test $F_n $TEST... " $N
@@ -10584,6 +10584,48 @@ PORT=$((PORT+1))
 N=$((N+1))
 
 
+# socat up to 1.7.2.0 and  2.0.0-b4 had a bug in xioscan_readline() that could
+# be exploited 
+# to overflow a heap based buffer (socat security advisory 3)
+# problem reported by Johan Thillemann
+NAME=READLINE_OVFL
+case "$TESTS" in
+*%functions%*|*%bugs%*|*%security%*|*%$NAME%*)
+TEST="$NAME: test for buffer overflow in readline prompt handling"
+# address 1 is the readline where write data was handled erroneous
+# address 2 provides data to trigger the buffer overflow
+# when no SIGSEGV or so occurs the test succeeded (bug fixed)
+if ! eval $NUMCOND; then :; else
+tf="$td/test$N.stdout"
+te="$td/test$N.stderr"
+ti="$td/test$N.data"
+CMD0="$SOCAT $opts READLINE $ti"
+printf "test $F_n $TEST... " $N
+# prepare long data - perl might not be installed
+#perl -e 'print "\r","Z"x513' >"$ti"
+echo $E -n "\rA" >"$ti"
+i=0; while [ $i -lt 32 ]; do echo -n "AAAAAAAAAAAAAAAA" >>"$ti"; let i=i+1; done
+$SOCAT - system:"$CMD0; echo rc=\$? >&2",pty >/dev/null 2>"${te}0"
+rc=$?
+rc0="$(grep ^rc= "${te}0" |sed 's/.*=//')"
+if [ $rc -ne 0 ]; then
+    $PRINTF "${YELLOW}framework failed${NORMAL}\n"
+elif [ $rc0 -eq 0 ]; then
+    $PRINTF "$OK\n"
+    numOK=$((numOK+1))
+else
+    $PRINTF "$FAILED\n"
+    echo "$CMD0"
+    grep -v ^rc= "${te}0"
+    numFAIL=$((numFAIL+1))
+fi
+fi # NUMCOND
+ ;;
+esac
+PORT=$((PORT+1))
+N=$((N+1))
+
+
 
 echo "summary: $((N-1)) tests; $numOK ok, $numFAIL failed, $numCANT could not be performed"
 
diff --git a/xio-readline.c b/xio-readline.c
index acd6eab..059f451 100644
--- a/xio-readline.c
+++ b/xio-readline.c
@@ -1,5 +1,5 @@
 /* source: xio-readline.c */
-/* Copyright Gerhard Rieger 2002-2009 */
+/* Copyright Gerhard Rieger 2002-2012 */
 /* Published under the GNU General Public License V.2, see file COPYING */
 
 /* this file contains the source for opening the readline address */
@@ -224,25 +224,26 @@ void xioscan_readline(struct single *pipe, const void *buff, size_t bytes) {
    if (pipe->dtype == XIODATA_READLINE && pipe->para.readline.dynprompt) {
       /* we save the last part of the output as possible prompt */
       const void *ptr = buff;
-      const void *pcr = memrchr(buff, '\r', bytes);
-      const void *plf = memrchr(buff, '\n', bytes);
+      const void *pcr;
+      const void *plf;
       size_t len;
+
       if (bytes > pipe->para.readline.dynbytes) {
 	 ptr = (const char *)buff + bytes - pipe->para.readline.dynbytes;
+	 len = pipe->para.readline.dynbytes;
+      } else {
+	 len = bytes;
       }
-      if (pcr) {
+      pcr = memrchr(ptr, '\r', len);
+      plf = memrchr(ptr, '\n', len);
+      if (pcr != NULL || plf != NULL) {
+	 const void *peol = Max(pcr, plf);
 	 /* forget old prompt */
 	 pipe->para.readline.dynend = pipe->para.readline.dynprompt;
+	 len -= (peol+1 - ptr);
 	 /* new prompt starts here */
-	 ptr = (const char *)pcr+1;
+	 ptr = (const char *)peol+1;
       }
-      if (plf && plf >= ptr) {
-	 /* forget old prompt */
-	 pipe->para.readline.dynend = pipe->para.readline.dynprompt;
-	 /* new prompt starts here */
-	 ptr = (const char *)plf+1;
-      }
-      len = (const char *)buff-(const char *)ptr+bytes;
       if (pipe->para.readline.dynend - pipe->para.readline.dynprompt + len >
 	  pipe->para.readline.dynbytes) {
 	 memmove(pipe->para.readline.dynprompt,
@@ -253,7 +254,6 @@ void xioscan_readline(struct single *pipe, const void *buff, size_t bytes) {
 	    pipe->para.readline.dynprompt + pipe->para.readline.dynbytes - len;
       }
       memcpy(pipe->para.readline.dynend, ptr, len);
-      /*pipe->para.readline.dynend = pipe->para.readline.dynprompt + len;*/
       pipe->para.readline.dynend = pipe->para.readline.dynend + len;
    }
    return;