The silc_pkcs1_decode function in the silccrypt library (silcpkcs1.c) in Secure Internet Live Conferencing (SILC) Toolkit before 1.1.7, SILC Client before 1.1.4, and SILC Server before 1.1.2 allows remote attackers to execute arbitrary code via a crafted PKCS#1 message, which triggers an integer underflow, signedness error, and a buffer overflow.  NOTE: the researcher describes this as an integer overflow, but CVE uses the "underflow" term in cases of wraparound from unsigned subtraction.