Several vulnerabilities have been discovered in asterisk, an Open Source PBX and telephony toolkit. The Common Vulnerabilities and Exposures project identifies the following problems: It is possible to determine valid login names via probing, due to the IAX2 response from asterisk . It is possible to determine a valid SIP username, when Digest authentication and authalwaysreject are enabled . It is possible to determine a valid SIP username via multiple crafted REGISTER messages . It was discovered that asterisk contains an obsolete copy of the Prototype JavaScript framework, which is vulnerable to several security issues. This copy is unused and now removed from asterisk . It was discovered that it is possible to perform a denial of service attack via RTP comfort noise payload with a long data length . The current version in oldstable is not supported by upstream anymore and is affected by several security issues. Backporting fixes for these and any future issues has become unfeasible and therefore we need to drop our security support for the version in oldstable. We recommend that all asterisk users upgrade to the stable distribution .