Multiple stack-based buffer overflows in libcURL and cURL 7.12.1, and possibly other versions, allow remote malicious web servers to execute arbitrary code via base64 encoded replies that exceed the intended buffer lengths when decoded, which is not properly handled by (1) the Curlinputntlm function in httpntlm.c during NTLM authentication or (2) the Curlkrbkauth and krb4auth functions in krb4.c during Kerberos authentication.