The nsAuthSSPI::Unwrap function in extensions/auth/nsAuthSSPI.cpp in Mozilla Thunderbird before 2.0.0.24 and SeaMonkey before 1.1.19 on Windows Vista, Windows Server 2008 R2, and Windows 7 allows remote SMTP, IMAP, and POP servers to cause a denial of service (heap memory corruption and application crash) or possibly execute arbitrary code via crafted data in a session that uses SSPI.