Joel R. Voss discovered that the IAX2 module of Asterisk, a free
software PBX and telephony toolkit performs insufficient validation of
IAX2 protocol messages, which may lead to denial of service.
For the stable distribution (etch), this problem has been fixed in
version 1.2.13~dfsg-2etch4.
For the unstable distribution (sid), this problem has been fixed
in version 1.4.19.1~dfsg-1.
We recommend that you upgrade your asterisk packages.