Several remote vulnerabilities have been discovered in Asterisk, a free software PBX and telephony toolkit. The Common Vulnerabilities and Exposures project identifies the following problems: Tilghman Lesher discovered that database-based registrations are insufficiently validated. This only affects setups, which are configured to run without a password and only host-based authentication. Jason Parker discovered that insufficient validation of From: headers inside the SIP channel driver may lead to authentication bypass and the potential external initiation of calls. This update also fixes a format string vulnerability, which can only be triggered through configuration files under control of the local administrator. In later releases of Asterisk this issue is remotely exploitable and tracked as CVE-2008-1333. The status of the old stable distribution (sarge) is currently being investigated. If affected, an update will be released through security.debian.org.