The Open Phone Abstraction Library (opal), as used by (1) Ekiga before 2.0.10 and (2) OpenH323 before 2.2.4, allows remote attackers to cause a denial of service (crash) via an invalid Content-Length header field in Session Initiation Protocol (SIP) packets, which causes a \0 byte to be written to an "attacker-controlled address."

Multiple vulnerabilities in PWLib before 1.6.0 allow remote attackers to cause a denial of service and possibly execute arbitrary code, as demonstrated by the NISCC/OUSPG PROTOS test suite for the H.225 protocol.