diff -Naur capi20.orig/capiutils.h capi20/capiutils.h
--- capi20.orig/capiutils.h	2005-03-22 16:16:34.000000000 +0100
+++ capi20/capiutils.h	2007-03-15 01:18:09.000000000 +0100
@@ -308,6 +308,10 @@
 #define capi20_cmd2str	capi_cmd2str
 char *capi_cmd2str(_cbyte cmd, _cbyte subcmd);
 
+/*
+ * WARNING: The following two functions use a single static buffer and
+ * are not thread-safe.
+ */
 #define capi20_cmsg2str	capi_cmsg2str
 char *capi_cmsg2str(_cmsg * cmsg);
 
diff -Naur capi20.orig/convert.c capi20/convert.c
--- capi20.orig/convert.c	2005-05-09 10:23:01.000000000 +0200
+++ capi20/convert.c	2007-03-15 01:20:13.000000000 +0100
@@ -894,10 +894,14 @@
 static void bufprint(char *fmt,...)
 {
 	va_list f;
+	size_t space = buf + sizeof(buf) - p, len;
 	va_start(f, fmt);
-	vsprintf(p, fmt, f);
+	len = vsnprintf(p, space, fmt, f);
 	va_end(f);
-	p += strlen(p);
+	if (len < space - 1)
+		p += len;
+	else
+		p += space - 1;
 }
 
 static void printstructlen(_cbyte * m, unsigned len)