Multiple stack-based buffer overflows in the Sieve plugin in Dovecot 1.0 before 1.0.4 and 1.1 before 1.1.7, as derived from Cyrus libsieve, allow context-dependent attackers to cause a denial of service (crash) and possibly execute arbitrary code via a crafted SIEVE script, as demonstrated by forwarding an e-mail message to a large number of recipients, a different vulnerability than CVE-2009-2632.