diff --git a/src/backend/libpq/be-secure.c b/src/backend/libpq/be-secure.c
index b3d00746eb9c195b2815968bf3181ca5148aec76..e3a7abc205ec254fdfb3ee7020bae562876a6c51 100644
--- a/src/backend/libpq/be-secure.c
+++ b/src/backend/libpq/be-secure.c
@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/libpq/be-secure.c,v 1.83.2.1 2009/01/28 15:06:57 mha Exp $
+ *	  $PostgreSQL: pgsql/src/backend/libpq/be-secure.c,v 1.83.2.2 2009/12/09 06:37:25 mha Exp $
  *
  *	  Since the server static private key ($DataDir/server.key)
  *	  will normally be stored unencrypted so that the database
@@ -938,9 +938,29 @@ aloop:
 		X509_NAME_oneline(X509_get_subject_name(port->peer),
 						  port->peer_dn, sizeof(port->peer_dn));
 		port->peer_dn[sizeof(port->peer_dn) - 1] = '\0';
-		X509_NAME_get_text_by_NID(X509_get_subject_name(port->peer),
+		r = X509_NAME_get_text_by_NID(X509_get_subject_name(port->peer),
 					   NID_commonName, port->peer_cn, sizeof(port->peer_cn));
 		port->peer_cn[sizeof(port->peer_cn) - 1] = '\0';
+		if (r == -1)
+		{
+			/* Unable to get the CN, set it to blank so it can't be used */
+			port->peer_cn[0] = '\0';
+		}
+		else
+		{
+			/*
+			 * Reject embedded NULLs in certificate common name to prevent attacks like
+			 * CVE-2009-4034.
+			 */
+			if (r != strlen(port->peer_cn))
+			{
+				ereport(COMMERROR,
+						(errcode(ERRCODE_PROTOCOL_VIOLATION),
+						 errmsg("SSL certificate's common name contains embedded null")));
+				close_SSL(port);
+				return -1;
+			}
+		}
 	}
 	ereport(DEBUG2,
 			(errmsg("SSL connection from \"%s\"", port->peer_cn)));
diff --git a/src/interfaces/libpq/fe-secure.c b/src/interfaces/libpq/fe-secure.c
index af919a8333e806cc2c62c2c08ebd1a9efb7fb9ae..a1aa046340720a791c7aef603fcd7dcecb9c8c09 100644
--- a/src/interfaces/libpq/fe-secure.c
+++ b/src/interfaces/libpq/fe-secure.c
@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/interfaces/libpq/fe-secure.c,v 1.102.2.1 2009/01/28 15:06:57 mha Exp $
+ *	  $PostgreSQL: pgsql/src/interfaces/libpq/fe-secure.c,v 1.102.2.2 2009/12/09 06:37:25 mha Exp $
  *
  * NOTES
  *	  [ Most of these notes are wrong/obsolete, but perhaps not all ]
@@ -1087,9 +1087,28 @@ open_client_SSL(PGconn *conn)
 					  conn->peer_dn, sizeof(conn->peer_dn));
 	conn->peer_dn[sizeof(conn->peer_dn) - 1] = '\0';
 
-	X509_NAME_get_text_by_NID(X509_get_subject_name(conn->peer),
+	r = X509_NAME_get_text_by_NID(X509_get_subject_name(conn->peer),
 							  NID_commonName, conn->peer_cn, SM_USER);
-	conn->peer_cn[SM_USER] = '\0';
+	conn->peer_cn[SM_USER] = '\0'; /* buffer is SM_USER+1 chars! */
+	if (r == -1)
+	{
+		/* Unable to get the CN, set it to blank so it can't be used */
+		conn->peer_cn[0] = '\0';
+	}
+	else
+	{
+		/*
+		 * Reject embedded NULLs in certificate common name to prevent attacks like
+		 * CVE-2009-4034.
+		 */
+		if (r != strlen(conn->peer_cn))
+		{
+			printfPQExpBuffer(&conn->errorMessage,
+							  libpq_gettext("SSL certificate's common name contains embedded null\n"));
+			close_SSL(conn);
+			return PGRES_POLLING_FAILED;
+		}
+	}
 
 	/* verify that the common name resolves to peer */