Ciprian Badescu found a SIGSEGV when doing multiple TFTP transfers using the multi interface, but I could also repeat it doing multiple sequential ones with the easy interface. Using Ciprian's test case, I could fix it. 
diff --git a/RELEASE-NOTES b/RELEASE-NOTES index 64c9fee..68c4e99 100644 --- a/RELEASE-NOTES +++ b/RELEASE-NOTES 
@@ -18,6 +18,8 @@  o proxy close during CONNECT authentication is now dealt with nicely  o the CURLOPT_DEBUGFUNCTION was sometimes called even when CURLOPT_VERBOSE  was not enabled + o multiple TFTP transfers on the same (easy or multi) handle could cause a + crash    Other curl-related news:   @@ -30,6 +32,7 @@  This release would not have looked like this without help, code, reports and  advice from friends like these:   - James Housley, Olaf Stueben, Yang Tse, Gisle Vanem, Bradford Bruce + James Housley, Olaf Stueben, Yang Tse, Gisle Vanem, Bradford Bruce, + Ciprian Badescu    Thanks! (and sorry if I forgot to mention someone)