Hi, while trying to investigate the bug I reported last week, I found that there is a broken boundary check in client_find_namespace in src/imap/imap-commands-util.c. The code is: /* make sure two hierarchy separators aren't next to each others */ for (p = storage_name+1; *p != '\0'; p++) { if (p[0] == ns->real_sep && p[-1] == ns->real_sep) { client_send_tagline(cmd, "NO Invalid mailbox name."); return NULL; } } The loop iterates over the string storage_name starting from its second byte. However, the string may be "". This is the case if you select the root of a namespace, like in "SELECT shared" or "SELECT shared/user1". In that case, the code will read past the end of the buffer from random memory until it finds a zero byte or a duplicate separator. This would fix it: diff -ru dovecot-2.0.15.orig/src/imap/imap-commands-util.c dovecot-2.0.15/src/imap/imap-commands-util.c --- dovecot-2.0.15.orig/src/imap/imap-commands-util.c 2011-08-02 12:29:37.000000000 +0200 +++ dovecot-2.0.15/src/imap/imap-commands-util.c 2011-09-26 18:33:16.121917759 +0200 @@ -81,7 +81,9 @@ } /* make sure two hierarchy separators aren't next to each others */ - for (p = storage_name+1; *p != '\0'; p++) { + for (p = storage_name; *p != '\0'; p++) { + if (p == storage_name) + continue; if (p[0] == ns->real_sep && p[-1] == ns->real_sep) { client_send_tagline(cmd, "NO Invalid mailbox name."); return NULL; Cheers, Christoph Bußenius -- Christoph Bußenius Rechnerbetriebsgruppe der Fakultäten Informatik und Mathematik TU München +49 89-289-18519 <> Raum 00.05.055 <> Boltzmannstr. 3 <> Garching