idiff -up openslp-2.0.0/common/slp_buffer.c.orig openslp-2.0.0/common/slp_buffer.c
--- openslp-2.0.0/common/slp_buffer.c.orig	2012-12-11 00:31:53.000000000 +0100
+++ openslp-2.0.0/common/slp_buffer.c	2019-12-09 10:39:16.422058793 +0100
@@ -153,4 +160,20 @@ void SLPBufferFree(SLPBuffer buf)
    xfree(buf);
 }
 
+/** Report remaining free buffer size in bytes.
+ *
+ * Check if buffer is allocated and if so return bytes left in a
+ * @c SLPBuffer object.
+ *
+ * @param[in] buf The SLPBuffer to be freed.
+ */
+size_t
+RemainingBufferSpace(SLPBuffer buf)
+{
+   if (buf->allocated == 0) {
+      return 0;
+   }
+   return buf->end - buf->curpos;
+}
+
 /*=========================================================================*/
diff -up openslp-2.0.0/common/slp_buffer.h.orig openslp-2.0.0/common/slp_buffer.h
--- openslp-2.0.0/common/slp_buffer.h.orig	2012-11-28 18:07:04.000000000 +0100
+++ openslp-2.0.0/common/slp_buffer.h	2019-12-09 10:39:16.422058793 +0100
@@ -78,6 +85,8 @@ SLPBuffer SLPBufferListRemove(SLPBuffer

 SLPBuffer SLPBufferListAdd(SLPBuffer * list, SLPBuffer buf);
 
+size_t RemainingBufferSpace(SLPBuffer buf);
+
 /*! @} */
 
 #endif /* SLP_BUFFER_H_INCLUDED */
diff -up openslp-2.0.0/slpd/slpd_process.c.orig openslp-2.0.0/slpd/slpd_process.c
--- openslp-2.0.0/slpd/slpd_process.c.orig	2019-12-09 10:39:16.420058789 +0100
+++ openslp-2.0.0/slpd/slpd_process.c	2019-12-09 10:39:16.422058793 +0100
@@ -523,13 +530,27 @@ RESPOND:
    {
       for (i = 0; i < db->urlcount; i++)
       {
-         /* urlentry is the url from the db result */
          urlentry = db->urlarray[i];
+         if (urlentry->opaque != NULL) {
+            const int64_t newsize = size + urlentry->opaquelen;
+            if (urlentry->opaquelen <= 0 || newsize > INT_MAX)
+            {
+               SLPDLog("Invalid opaquelen %d or sizeo of opaque url is too big, size=%d\n",
+                       urlentry->opaquelen, size);
+               errorcode = SLP_ERROR_PARSE_ERROR;
+               goto FINISHED;
+            }
+            size +=  urlentry->opaquelen;
+         }
+         else
+         {
+            /* urlentry is the url from the db result */
+            size += urlentry->urllen + 6; /*  1 byte for reserved  */
+                                          /*  2 bytes for lifetime */
+                                          /*  2 bytes for urllen   */
+                                          /*  1 byte for authcount */
+          }

-         size += urlentry->urllen + 6; /*  1 byte for reserved  */
-                                       /*  2 bytes for lifetime */
-                                       /*  2 bytes for urllen   */
-                                       /*  1 byte for authcount */
 #ifdef ENABLE_SLPv2_SECURITY
          /* make room to include the authblock that was asked for */
          if (G_SlpdProperty.securityEnabled
@@ -603,7 +624,7 @@ RESPOND:
          urlentry = db->urlarray[i];
 
 #ifdef ENABLE_SLPv1
-         if (urlentry->opaque == 0)
+         if (urlentry->opaque == NULL)
          {
             /* url-entry reserved */
             *result->curpos++ = 0;
@@ -615,8 +636,18 @@ RESPOND:
             PutUINT16(&result->curpos, urlentry->urllen);
 
             /* url-entry url */
-            memcpy(result->curpos, urlentry->url, urlentry->urllen);
-            result->curpos += urlentry->urllen;
+            if (RemainingBufferSpace(result) >= urlentry->urllen)
+            {
+               memcpy(result->curpos, urlentry->url, urlentry->urllen);
+               result->curpos = result->curpos + urlentry->urllen;
+            }
+            else
+            {
+                SLPDLog("Url too big (ask: %d have %" PRId64 "), failing request\n",
+                        urlentry->opaquelen, (int64_t) RemainingBufferSpace(result));
+                errorcode = SLP_ERROR_PARSE_ERROR;
+                goto FINISHED;
+            }
 
             /* url-entry auths */
             *result->curpos++ = 0;
@@ -628,14 +659,24 @@ RESPOND:

             /* TRICKY: Fix up the lifetime. */
             TO_UINT16(urlentry->opaque + 1, urlentry->lifetime);
-            memcpy(result->curpos, urlentry->opaque, urlentry->opaquelen);
-
-            /* TRICKY: Fix up the result authblock count. */
-            if (urlentry->authcount)
-                result->curpos[1 + 2 + 2 + urlentry->urllen] = (uint8_t)urlentry->authcount;
-                /* 1 reserved + 2 lifetime + 2 url length */
-
-            result->curpos += urlentry->opaquelen;
+            if (RemainingBufferSpace(result) >= urlentry->opaquelen)
+            {
+               memcpy(result->curpos, urlentry->opaque, urlentry->opaquelen);
+
+              /* TRICKY: Fix up the result authblock count. */
+              if (urlentry->authcount)
+                  result->curpos[1 + 2 + 2 + urlentry->urllen] = (uint8_t)urlentry->authcount;
+                  /* 1 reserved + 2 lifetime + 2 url length */
+
+               result->curpos = result->curpos + urlentry->opaquelen;
+             }
+             else
+             {
+               SLPDLog("Opaque Url too big (ask: %d have %" PRId64 "), failing request\n",
+                       urlentry->opaquelen, (int64_t) RemainingBufferSpace(result));
+               errorcode = SLP_ERROR_PARSE_ERROR;
+               goto FINISHED;
+             }
          }
       }
    }
